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SQL SERVER BPSORT WAIT Extended Events wait_type value: Maps to the BATCH_MODE_SORT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 1062 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH Extended Events latch_class value: Maps to the DATASET_PARENT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 7 in 2008 and 2008 R2, and 1 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or changing the configuration of an availability group. ( Books Online description: “Occurs when an AlwaysOn DDL statement or Windows Server Failover Clustering commandis waiting
AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes it easier to do. SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER FT_IFTSHC_MUTEX WAIT Description: This wait is when a thread that is participating in a full-text operation is waiting for synchronization with other full-text worker threads. ( Books Online description: “Full-text is waiting on an fdhost control operation. Documented for informationalpurposes only.
SQL SERVER BPSORT WAIT Extended Events wait_type value: Maps to the BATCH_MODE_SORT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 1062 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQLSKILLS SQL101: PARTITIONING SQLskills SQL101: Partitioning. Kimberly Tripp. March 27, 2017. Continuing on our path to understanding the basics and core concepts, there’s a big topic that’s often greatly misunderstood and that’s partitioning. I know I’m going to struggle keeping this one an introductory post but I’ve decided there are a few criticalquestions to
SQL SERVER PREEMPTIVE_COM_GETDATA WAIT Other information: If this wait type becomes prevalent, determine the query that is causing the wait and analyze the performance of the code of the COM object being used. Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes it easier to do. SQL SERVER REDO_THREAD_PENDING_WORK WAIT Extended Events wait_type value: Maps to the REDO_SIGNAL map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here ). The map_key value in sys.dm_xe_map_values is 752 in 2012 and 770 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER NESTING_TRANSACTION_FULL LATCH Description: This latch class, along with NESTING_TRANSACTION_READONLY, is used to control access to the transaction description structure (called an XDES) for the parent transaction of a parallel nested transaction. A query that involves a parallel operator must start a sub-transaction for each parallel thread that is used, so these SQL SERVER LCK_M_U WAIT Specific guidance for LCK_M_U waits: For an Update lock, the resource could be a row, page, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. As this lock is in preparation for conversion to an Exclusive lock, troubleshoot as ifyou were
SQL SERVER PREEMPTIVE_OS_FILEOPS WAIT I have not seen this wait type be a noticeable contention point. Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with thethread.
SQL SERVER RESOURCE_SEMAPHORE_QUERY_COMPILE WAIT Description: This wait type is when a thread is waiting for availability at the next higher query compilation memory gateway. Queries start compiling with no memory limit, and as a query’s compilation takes more and more memory, compilation will be stalled at each of three gateways (small, medium, and large) that limit the number of concurrently compiling queries that are using more than a SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER FT_IFTSHC_MUTEX WAIT Description: This wait is when a thread that is participating in a full-text operation is waiting for synchronization with other full-text worker threads. ( Books Online description: “Full-text is waiting on an fdhost control operation. Documented for informationalpurposes only.
SQL SERVER BPSORT WAIT Extended Events wait_type value: Maps to the BATCH_MODE_SORT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 1062 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH Extended Events latch_class value: Maps to the DATASET_PARENT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 7 in 2008 and 2008 R2, and 1 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER FT_IFTSHC_MUTEX WAIT Description: This wait is when a thread that is participating in a full-text operation is waiting for synchronization with other full-text worker threads. ( Books Online description: “Full-text is waiting on an fdhost control operation. Documented for informationalpurposes only.
SQL SERVER BPSORT WAIT Extended Events wait_type value: Maps to the BATCH_MODE_SORT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 1062 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH Extended Events latch_class value: Maps to the DATASET_PARENT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 7 in 2008 and 2008 R2, and 1 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or changing the configuration of an availability group. ( Books Online description: “Occurs when an AlwaysOn DDL statement or Windows Server Failover Clustering commandis waiting
AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes it easier to do. SQLSKILLS SQL101: PARTITIONING SQLskills SQL101: Partitioning. Kimberly Tripp. March 27, 2017. Continuing on our path to understanding the basics and core concepts, there’s a big topic that’s often greatly misunderstood and that’s partitioning. I know I’m going to struggle keeping this one an introductory post but I’ve decided there are a few criticalquestions to
SQL SERVER NESTING_TRANSACTION_FULL LATCH Description: This latch class, along with NESTING_TRANSACTION_READONLY, is used to control access to the transaction description structure (called an XDES) for the parent transaction of a parallel nested transaction. A query that involves a parallel operator must start a sub-transaction for each parallel thread that is used, so these SQL SERVER LCK_M_IX WAIT Specific guidance for LCK_M_IX waits: For an Intent Exclusive lock, the resource could be a page, partition, or table. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the blocker is holding a table S lock, investigation why the blocking thread AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes it easier to do. SQL SERVER REDO_THREAD_PENDING_WORK WAIT Extended Events wait_type value: Maps to the REDO_SIGNAL map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here ). The map_key value in sys.dm_xe_map_values is 752 in 2012 and 770 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER LCK_M_U WAIT Specific guidance for LCK_M_U waits: For an Update lock, the resource could be a row, page, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. As this lock is in preparation for conversion to an Exclusive lock, troubleshoot as ifyou were
SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER PREEMPTIVE_OS_FILEOPS WAIT I have not seen this wait type be a noticeable contention point. Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with thethread.
SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER SOS_SCHEDULER_YIELD WAIT Description: This wait type is when a thread was able to execute for its full thread quantum (4 milliseconds in all versions of SQL Server, unchangeable), and so voluntarily yielded the scheduler, moving to the bottom of the Runnable Queue in its scheduler. SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER SP_SERVER_DIAGNOSTICS_SLEEP WAIT Description: This wait type is when the background system health monitor thread is waiting between checking whether to run the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. SQL SERVER PREEMPTIVE_OS_WRITEFILEGATHER WAIT Description: This wait type is when a thread is calling the Windows WriteFileGather function. (Books Online description: N/A)Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.. Added in SQL Server version: 2008 SQL SERVER LCK_M_X WAIT Specific guidance for LCK_M_X waits: For an Exclusive lock, the resource could be a row, page, partition, table, file, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the blocker is holding a table S lock, investigationwhy the
SQL SERVER REDO_THREAD_PENDING_WORK WAIT Extended Events wait_type value: Maps to the REDO_SIGNAL map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here ). The map_key value in sys.dm_xe_map_values is 752 in 2012 and 770 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER FT_IFTSHC_MUTEX WAIT Description: This wait is when a thread that is participating in a full-text operation is waiting for synchronization with other full-text worker threads. ( Books Online description: “Full-text is waiting on an fdhost control operation. Documented for informationalpurposes only.
SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER WRITELOG WAIT Description: This wait type is when a thread is waiting for a log block to be written to disk by an asynchronous I/O. A log block is written to disk when: A transaction commits (unless it is set to be delayed durable in SQL Server 2014 and above) The log block reaches its maximum size of 60Kb. A data file page is being written to diskand write
SQL SERVER LCK_M_X WAIT Specific guidance for LCK_M_X waits: For an Exclusive lock, the resource could be a row, page, partition, table, file, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the blocker is holding a table S lock, investigationwhy the
SQL SERVER SP_SERVER_DIAGNOSTICS_SLEEP WAIT Description: This wait type is when the background system health monitor thread is waiting between checking whether to run the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER PAGEIOLATCH_EX WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to modify the page structure once it is in memory (EX = EXclusive mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with other latch modes. SQL SERVER SOS_SCHEDULER_YIELD WAIT Description: This wait type is when a thread was able to execute for its full thread quantum (4 milliseconds in all versions of SQL Server, unchangeable), and so voluntarily yielded the scheduler, moving to the bottom of the Runnable Queue in its scheduler. SQL SERVER PAGELATCH_UP WAIT Description: This wait type is when a thread is waiting for access to a data file page in memory (usually an allocation bitmap page) so that it can update the page structure (UP = UPdate mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with other latch modes. IMPORTANT CHANGE TO VLF CREATION ALGORITHM IN SQL SERVER Since SQL server 2014 was released back in April last year, there have been some rumblings about changes to how many VLFs are created when the log is grown or auto-grown (I’ll just say auto-grown from now on, as that’s the most common scenario). I experimented a bit and thought I’d figured out the algorithm SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER SP_SERVER_DIAGNOSTICS_SLEEP WAIT Description: This wait type is when the background system health monitor thread is waiting between checking whether to run the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER WRITELOG WAIT Description: This wait type is when a thread is waiting for a log block to be written to disk by an asynchronous I/O. A log block is written to disk when: A transaction commits (unless it is set to be delayed durable in SQL Server 2014 and above) The log block reaches its maximum size of 60Kb. A data file page is being written to diskand write
SQL SERVER LCK_M_X WAIT Specific guidance for LCK_M_X waits: For an Exclusive lock, the resource could be a row, page, partition, table, file, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the blocker is holding a table S lock, investigationwhy the
SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER LCK_M_S WAIT Specific guidance for LCK_M_S waits: For a Shared lock, the resource could be a row, page, partition, table, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the resource is a table, any update or insert to the table will require a SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER SP_SERVER_DIAGNOSTICS_SLEEP WAIT Description: This wait type is when the background system health monitor thread is waiting between checking whether to run the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. SQL SERVER WRITELOG WAIT Description: This wait type is when a thread is waiting for a log block to be written to disk by an asynchronous I/O. A log block is written to disk when: A transaction commits (unless it is set to be delayed durable in SQL Server 2014 and above) The log block reaches its maximum size of 60Kb. A data file page is being written to diskand write
SQL SERVER LCK_M_X WAIT Specific guidance for LCK_M_X waits: For an Exclusive lock, the resource could be a row, page, partition, table, file, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. If the blocker is holding a table S lock, investigationwhy the
SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER SP_SERVER_DIAGNOSTICS_SLEEP WAIT Description: This wait type is when the background system health monitor thread is waiting between checking whether to run the sp_server_diagnostics procedure. This was added for SQL Server 2012 to aid with automatic detection of failures to allow automatic failover with availability groups. SQL SERVER BPSORT WAIT Extended Events wait_type value: Maps to the BATCH_MODE_SORT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 1062 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH Extended Events latch_class value: Maps to the DATASET_PARENT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 7 in 2008 and 2008 R2, and 1 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. IMPORTANT CHANGE TO VLF CREATION ALGORITHM IN SQL SERVER Since SQL server 2014 was released back in April last year, there have been some rumblings about changes to how many VLFs are created when the log is grown or auto-grown (I’ll just say auto-grown from now on, as that’s the most common scenario). I experimented a bit and thought I’d figured out the algorithm SQL SERVER HADR_WORK_QUEUE WAIT Description: This wait type is when a thread is waiting for some work to be entered into the AG work queue. (Books Online description: “AlwaysOn Availability Groups background worker thread waiting for new work to be assigned.This is an expected wait when there are ready workers waiting for new work, which is the normal state.”) SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER REDO_THREAD_PENDING_WORK WAIT Extended Events wait_type value: Maps to the REDO_SIGNAL map_value in sys.dm_xe_map_values (thanks to Jonathan’s post here ). The map_key value in sys.dm_xe_map_values is 752 in 2012 and 770 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER SOS_SCHEDULER_YIELD WAIT Description: This wait type is when a thread was able to execute for its full thread quantum (4 milliseconds in all versions of SQL Server, unchangeable), and so voluntarily yielded the scheduler, moving to the bottom of the Runnable Queue in its scheduler. SQL SERVER PAGELATCH_UP WAIT Description: This wait type is when a thread is waiting for access to a data file page in memory (usually an allocation bitmap page) so that it can update the page structure (UP = UPdate mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with other latch modes. SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-modeprocessing.
SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER ONDEMAND_TASK_QUEUE WAIT Description: As stated below. One example of high-priority system task request is a DTC commit/abort. (Books Online description: “Occurs while a background task waits for high priority system task requests.Long wait times indicate that there have been no high priority requests to process, and should not cause concern.”) SQL SERVER SOS_WORK_DISPATCHER WAIT Description: This wait type is where a thread in SQLOS is waiting for something to do. This wait starts when the thread becomes idle and stops when the thread is given some work to do. SQL SERVER LCK_M_S WAIT Description: This wait type is when a thread is waiting to acquire a Shared lock on a resource and there is at least one other lock in an incompatible mode granted on the resource to a different thread. SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH This page explains the ACCESS_METHODS_DATASET_PARENT latch class and gives examples of where it occurs in SQL Server. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT Description: This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-modeprocessing.
SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER ONDEMAND_TASK_QUEUE WAIT Description: As stated below. One example of high-priority system task request is a DTC commit/abort. (Books Online description: “Occurs while a background task waits for high priority system task requests.Long wait times indicate that there have been no high priority requests to process, and should not cause concern.”) SQL SERVER SOS_WORK_DISPATCHER WAIT Description: This wait type is where a thread in SQLOS is waiting for something to do. This wait starts when the thread becomes idle and stops when the thread is given some work to do. SQL SERVER LCK_M_S WAIT Description: This wait type is when a thread is waiting to acquire a Shared lock on a resource and there is at least one other lock in an incompatible mode granted on the resource to a different thread. SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH This page explains the ACCESS_METHODS_DATASET_PARENT latch class and gives examples of where it occurs in SQL Server. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT Description: This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or AUTOGROW ALL FILES FEATURE IN SSMS 18.0 PREVIEW 4 One of the small improvements in SSMS 18.0 Preview 4 is the addition of an “Autogrow All Files” checkbox in the Database Properties dialog on Filegroups page as shown in Figure 1. This is another nice change that will hopefully make it easier for more people to enable this setting because the tooling actually makes SQL SERVER JUMPSTART+ BUNDLE SQL Server Jumpstart+ Bundle Your SQL Server Jumpstart+ Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: SQLskills IE0: Immersion Event for the Accidental and Junior DBA SQLskills IEQuery: Immersion Event on Fixing Slow Queries, Inefficient Code, and Caching/Statistics Problems SQLskills IETLB: Immersion Event on Transactions, Locking SQL SERVER JUMPSTART BUNDLE SQL Server Jumpstart Bundle Your SQL Server Jumpstart Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: SQLskills IE0: Immersion Event for the Accidental and Junior DBA SQLskills IEQuery: Immersion Event on Fixing Slow Queries, Inefficient Code, and Caching/Statistics Problems SQLskills IETLB: Immersion Event on Transactions, Locking SQL SERVER PERFORMANCE TUNING BUNDLE SQL Server Performance Tuning Bundle Your SQL Server Performance Tuning Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: IEPTO1: Immersion Event on Performance Tuning and Optimization – Part 1 IEPTO2: Immersion Event on Performance Tuning and Optimization – Part 2 SQLSKILLS BLACKBELT BUNDLE SQLskills Blackbelt Bundle SQLskills IEAzure: Immersion Event on Azure SQL Database, VMs, Azure Managed Instance SQLskills IEPTO1: Immersion Event on Performance Tuning and Optimization, Part 1 SQLskills IEPTO2: Immersion Event on Performance Tuning and Optimization, Part 2 SQLskills IECAG: Immersion Event on Clustering and Availability Groups SQLskills IEQS: Immersion Event on Solving SQLSKILLS SQL101: PARTITIONING One thing that simplifies the choice of Views/Tables is the SQL Edition. At least through 2014 PT are Enterprise only and some of us are still limited Standard :). SQL SERVER NESTING_TRANSACTION_FULL LATCH This page explains the NESTING_TRANSACTION_FULL latch class and gives examples of where it occurs in SQL Server. SQL SERVER RESOURCE_SEMAPHORE WAIT Description: This wait type is when a thread is waiting for a query execution memory grant so it can begin executing. Memory grants are used for performing query operations like sorts and hashes. SQL SERVER PAGELATCH_UP WAIT Description: This wait type is when a thread is waiting for access to a data file page in memory (usually an allocation bitmap page) so that it can update the page structure (UP = UPdate mode). SQL SERVER RESOURCE_SEMAPHORE_QUERY_COMPILE WAIT Description: This wait type is when a thread is waiting for availability at the next higher query compilation memory gateway. Queries start compiling with no memory limit, and as a query’s compilation takes more and more memory, compilation will be stalled at each of three gateways (small, medium, and large) that limit the number of concurrently compiling queries that are using more than a SQL SERVER VDI_CLIENT_OTHER WAIT Description: This wait type is when a thread is waiting for more work when seeding a new availability group replica, or in Azure when something triggers a database copy, like changing a service tier or setting up geo-replication. SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER LCK_M_U WAIT Specific guidance for LCK_M_U waits: For an Update lock, the resource could be a row, page, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. As this lock is in preparation for conversion to an Exclusive lock, troubleshoot as ifyou were
SQL SERVER CMEMTHREAD WAIT Here, where servers with more than 8 cores per NUMA node may require trace flag 8048. Note also that in SQL Server 2016, CMemThread objects will dynamically be promoted to per-NUMA node or per-CPU when contention is detected (i.e. a superset of the TF 8048 behavior). This should mean that CMEMTHREAD waits become less of an issue on SQLServer 2016.
SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or changing the configuration of an availability group. ( Books Online description: “Occurs when an AlwaysOn DDL statement or Windows Server Failover Clustering commandis waiting
SQL SERVER PREEMPTIVE_OS_LOOKUPACCOUNTSID WAIT So while it’s more common that a local DC or ADC has an issue, it could also be a long round-trip time for the security information. Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as SQL SERVER TRAINING & CONSULTING FOR DBAS & DEVELOPERSTRAININGSERVICESRESOURCESABOUT USOUR BLOGSWHAT’S NEW Your career is built on keeping your company’s servers and applications up and running. That wouldn’t be so worrisome except for one thing: the data platform industry is changing faster than you can keep up. When something breaks and you don’t have up-to-date training, one of two things typically happens: You waste time chasing SQL SERVER CXCONSUMER WAIT Description: The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in 2016 SP2 and 2017 RTM CU3 (as a result of a Connect item I submitted in 2016) to reduce the number of actionable CXPACKET waits that occur. The idea is that benign CXPACKET waits now show up as CXCONSUMER waits and can usually be safely ignored (but see below) SQL SERVER HTDELETE WAIT Description: This wait type (and the other HT* waits) is when a thread is waiting for access to the shared hash table used during batch-mode processing. SQL Server 2012 used to use a hash table per thread and SQL Server 2014 now uses a shared hash table. This change was made to reduce the amount of memory required for the hash table, but comes SQL SERVER SOS_WORK_DISPATCHER WAIT This page explains the SOS_WORK_DISPATCHER wait type and gives examples of where it occurs in SQL Server. SQL SERVER LCK_M_U WAIT Specific guidance for LCK_M_U waits: For an Update lock, the resource could be a row, page, or database. Common blockers are a table X (Exclusive) lock from lock escalation occurring, or a SCH_M (Schema Modification) lock from an index build/rebuild. As this lock is in preparation for conversion to an Exclusive lock, troubleshoot as ifyou were
SQL SERVER CMEMTHREAD WAIT Here, where servers with more than 8 cores per NUMA node may require trace flag 8048. Note also that in SQL Server 2016, CMemThread objects will dynamically be promoted to per-NUMA node or per-CPU when contention is detected (i.e. a superset of the TF 8048 behavior). This should mean that CMEMTHREAD waits become less of an issue on SQLServer 2016.
SQL SERVER DISPATCHER_QUEUE_SEMAPHORE WAIT This wait type is when a thread from a special dispatcher pool is waiting for work to do. Parts of SQL Server that I know use their own thread pool is the backup subsystem and the In-Memory OLTP system in the Storage Engine. ( Books Online description: “Occurs when a thread from the dispatcher pool is waiting for more work to process. SQL SERVER PAGEIOLATCH_SH WAIT Description: This wait type is when a thread is waiting for the read of a data file page from disk to complete, and the thread is going to read (not modify) the page structure once it is in memory (SH = SHare mode). The Latches Whitepaper in the sidebar on the right has a description of all latch modes and their compatibility with otherlatch
SQL SERVER HADR_AG_MUTEX WAIT Description: This wait type is when a thread is waiting for access to a critical section of code (one which only one thread can be executing) as part of examining or changing the configuration of an availability group. ( Books Online description: “Occurs when an AlwaysOn DDL statement or Windows Server Failover Clustering commandis waiting
SQL SERVER PREEMPTIVE_OS_LOOKUPACCOUNTSID WAIT So while it’s more common that a local DC or ADC has an issue, it could also be a long round-trip time for the security information. Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as SQL SERVER JUMPSTART BUNDLE SQL Server Jumpstart Bundle Your SQL Server Jumpstart Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: SQLskills IE0: Immersion Event for the Accidental and Junior DBA SQLskills IEQuery: Immersion Event on Fixing Slow Queries, Inefficient Code, and Caching/Statistics Problems SQLskills IETLB: Immersion Event on Transactions, Locking SQL SERVER JUMPSTART+ BUNDLE SQL Server Jumpstart+ Bundle Your SQL Server Jumpstart+ Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: SQLskills IE0: Immersion Event for the Accidental and Junior DBA SQLskills IEQuery: Immersion Event on Fixing Slow Queries, Inefficient Code, and Caching/Statistics Problems SQLskills IETLB: Immersion Event on Transactions, Locking SQLSKILLS BLACKBELT BUNDLE SQLskills Blackbelt Bundle SQLskills IEAzure: Immersion Event on Azure SQL Database, VMs, Azure Managed Instance SQLskills IEPTO1: Immersion Event on Performance Tuning and Optimization, Part 1 SQLskills IEPTO2: Immersion Event on Performance Tuning and Optimization, Part 2 SQLskills IECAG: Immersion Event on Clustering and Availability Groups SQLskills IEQS: Immersion Event on Solving SQL SERVER PERFORMANCE TUNING BUNDLE SQL Server Performance Tuning Bundle Your SQL Server Performance Tuning Bundle is available NOW; your course membership includes access to these recorded courses for 1 year: IEPTO1: Immersion Event on Performance Tuning and Optimization – Part 1 IEPTO2: Immersion Event on Performance Tuning and Optimization – Part 2 SQLSKILLS SQL101: PARTITIONING SQLskills SQL101: Partitioning. Kimberly Tripp. March 27, 2017. Continuing on our path to understanding the basics and core concepts, there’s a big topic that’s often greatly misunderstood and that’s partitioning. I know I’m going to struggle keeping this one an introductory post but I’ve decided there are a few criticalquestions to
SQL SERVER WRITELOG WAIT Description: This wait type is when a thread is waiting for a log block to be written to disk by an asynchronous I/O. A log block is written to disk when: A transaction commits (unless it is set to be delayed durable in SQL Server 2014 and above) The log block reaches its maximum size of 60Kb. A data file page is being written to diskand write
SQL SERVER ACCESS_METHODS_DATASET_PARENT LATCH Extended Events latch_class value: Maps to the DATASET_PARENT map_value in sys.dm_xe_map_values. The map_key value in sys.dm_xe_map_values is 7 in 2008 and 2008 R2, and 1 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds. SQL SERVER ASYNC_NETWORK_IO WAIT A simple test for network issues is to test the ping time between the SQL Server and the client/application/web server, and if the ping time is close to the average wait time, then the wait is because of the network (which may just be the normal network latency, not necessarily a problem). There is usually nothing that you can do with your SQL SQL SERVER HADR_FILESTREAM_IOMGR_IOCOMPLETION WAIT Description: This wait type is when the FILESTREAM I/O manager for availability groups is sleeping between checks for completion of any I/Os sending FILESTREAM data to replicas. This wait occurs every 0.5 seconds for 0.5 seconds, regardless of whether any availability groups are configured. ( Books Online description: “The FILESTREAM AlwaysOn SQL SERVER COLUMNSTORE_BUILD_THROTTLE WAIT Then the memory grants are given per thread and the other segments are built multi-threaded. Although all the threads for the operation are allocated at the start of the build, only one thread is used for the first segment and all the others incur a COLUMNSTORE_BUILD_THROTTLE wait. If the build of the first segment is taking a long time, the* Training__
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