Update sql-server-deadlocks-guide.md

AnnaMHuff · web-flow · commit a56780a6f01d · 2023-10-10T11:50:04.000-06:00
Acrolinx replace "may" with "might"
diff --git a/docs/relational-databases/sql-server-deadlocks-guide.md b/docs/relational-databases/sql-server-deadlocks-guide.md
@@ -35,7 +35,7 @@ Both transactions in a deadlock will wait forever unless the deadlock is broken
   
 Deadlocking is often confused with normal blocking. When a transaction requests a lock on a resource locked by another transaction, the requesting transaction waits until the lock is released. By default, [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] transactions do not time out, unless LOCK_TIMEOUT is set. The requesting transaction is blocked, not deadlocked, because the requesting transaction has not done anything to block the transaction owning the lock. Eventually, the owning transaction will complete and release the lock, and then the requesting transaction will be granted the lock and proceed. Deadlocks are resolved almost immediately, whereas blocking can, in theory, persist indefinitely. Deadlocks are sometimes called a deadly embrace.  
   
-Deadlock is a condition that can occur on any system with multiple threads, not just on a relational database management system, and can occur for resources other than locks on database objects. For example, a thread in a multithreaded operating system might acquire one or more resources, such as blocks of memory. If the resource being acquired is currently owned by another thread, the first thread may have to wait for the owning thread to release the target resource. The waiting thread is said to have a dependency on the owning thread for that particular resource. In an instance of the [!INCLUDE[ssDEnoversion](../includes/ssdenoversion-md.md)], sessions can deadlock when acquiring non-database resources, such as memory or threads.  
+Deadlock is a condition that can occur on any system with multiple threads, not just on a relational database management system, and can occur for resources other than locks on database objects. For example, a thread in a multithreaded operating system might acquire one or more resources, such as blocks of memory. If the resource being acquired is currently owned by another thread, the first thread might have to wait for the owning thread to release the target resource. The waiting thread is said to have a dependency on the owning thread for that particular resource. In an instance of the [!INCLUDE[ssDEnoversion](../includes/ssdenoversion-md.md)], sessions can deadlock when acquiring non-database resources, such as memory or threads.  
   
 :::image type="content" source="media/sql-server-deadlocks-guide/deadlock.png" alt-text="Diagram showing a transaction deadlock." lightbox="media/sql-server-deadlocks-guide/deadlock.png":::
   
@@ -65,7 +65,7 @@ Each user session might have one or more tasks running on its behalf where each
   
 -   **Memory**. When concurrent requests are waiting for memory grants that cannot be satisfied with the available memory, a deadlock can occur. For example, two concurrent queries, Q1 and Q2, execute as user-defined functions that acquire 10 MB and 20 MB of memory respectively. If each query needs 30 MB and the total available memory is 20 MB, then Q1 and Q2 must wait for each other to release memory, and this results in a deadlock.  
   
--   **Parallel query execution-related resources**. Coordinator, producer, or consumer threads associated with an exchange port may block each other causing a deadlock usually when including at least one other process that is not a part of the parallel query. Also, when a parallel query starts execution, [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] determines the degree of parallelism, or the number of worker threads, based upon the current workload. If the system workload unexpectedly changes, for example, where new queries start running on the server or the system runs out of worker threads, then a deadlock could occur.  
+-   **Parallel query execution-related resources**. Coordinator, producer, or consumer threads associated with an exchange port might block each other causing a deadlock usually when including at least one other process that is not a part of the parallel query. Also, when a parallel query starts execution, [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] determines the degree of parallelism, or the number of worker threads, based upon the current workload. If the system workload unexpectedly changes, for example, where new queries start running on the server or the system runs out of worker threads, then a deadlock could occur.  
   
 -   **Multiple Active Result Sets (MARS) resources**. These resources are used to control interleaving of multiple active requests under MARS. For more information, see [Using Multiple Active Result Sets (MARS)](../relational-databases/native-client/features/using-multiple-active-result-sets-mars.md).  
   
@@ -221,14 +221,14 @@ For more information, see [Use the system_health Session](../relational-database
 When deadlocks occur, Trace Flag 1204 and Trace Flag 1222 return information that is captured in the [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] error log. Trace Flag 1204 reports deadlock information formatted by each node involved in the deadlock. Trace Flag 1222 formats deadlock information, first by processes and then by resources. It is possible to enable both trace flags to obtain two representations of the same deadlock event.  
 
 > [!IMPORTANT]
-> Avoid using Trace Flag 1204 and 1222 on workload-intensive systems that are experiencing deadlocks. Using these trace flags may introduce performance issues. Instead, use the [Deadlock Extended Event](#deadlock_xevent) to capture the necessary information.
+> Avoid using Trace Flag 1204 and 1222 on workload-intensive systems that are experiencing deadlocks. Using these trace flags might introduce performance issues. Instead, use the [Deadlock Extended Event](#deadlock_xevent) to capture the necessary information.
   
 In addition to defining the properties of Trace Flag 1204 and 1222, the following table also shows the similarities and differences.  
   
 |Property|Trace Flag 1204 and Trace Flag 1222|Trace Flag 1204 only|Trace Flag 1222 only|  
 |--------------|-----------------------------------------|--------------------------|--------------------------|  
 |Output format|Output is captured in the [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] error log.|Focused on the nodes involved in the deadlock. Each node has a dedicated section, and the final section describes the deadlock victim.|Returns information in an XML-like format that does not conform to an XML Schema Definition (XSD) schema. The format has three major sections. The first section declares the deadlock victim. The second section describes each process involved in the deadlock. The third section describes the resources that are synonymous with nodes in Trace Flag 1204.|  
-|Identifying attributes|**SPID:<x\> ECID:<x\>.** Identifies the system process ID thread in cases of parallel processes. The entry `SPID:<x> ECID:0`, where <x\> is replaced by the SPID value, represents the main thread. The entry `SPID:<x> ECID:<y>`, where <x\> is replaced by the SPID value and <y\> is greater than 0, represents the subthreads for the same SPID.<br /><br /> **BatchID** (**sbid** for Trace Flag 1222). Identifies the batch from which code execution is requesting or holding a lock. When Multiple Active Result Sets (MARS) is disabled, the BatchID value is 0. When MARS is enabled, the value for active batches is 1 to *n*. If there are no active batches in the session, BatchID is 0.<br /><br /> **Mode**. Specifies the type of lock for a particular resource that is requested, granted, or waited on by a thread. Mode can be IS (Intent Shared), S (Shared), U (Update), IX (Intent Exclusive), SIX (Shared with Intent Exclusive), and X (Exclusive).<br /><br /> **Line #** (**line** for Trace Flag 1222). Lists the line number in the current batch of statements that was being executed when the deadlock occurred.<br /><br /> **Input Buf** (**inputbuf** for Trace Flag 1222). Lists all the statements in the current batch.|**Node**. Represents the entry number in the deadlock chain.<br /><br /> **Lists**. The lock owner can be part of these lists:<br /><br /> **Grant List**. Enumerates the current owners of the resource.<br /><br /> **Convert List**. Enumerates the current owners that are trying to convert their locks to a higher level.<br /><br /> **Wait List**. Enumerates current new lock requests for the resource.<br /><br /> **Statement Type**. Describes the type of DML statement (SELECT, INSERT, UPDATE, or DELETE) on which the threads have permissions.<br /><br /> **Victim Resource Owner**. Specifies the participating thread that [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] chooses as the victim to break the deadlock cycle. The chosen thread and all existing subthreads are terminated.<br /><br /> **Next Branch**. Represents the two or more subthreads from the same SPID that are involved in the deadlock cycle.|**deadlock victim**. Represents the physical memory address of the task (see [sys.dm_os_tasks (Transact-SQL)](../relational-databases/system-dynamic-management-views/sys-dm-os-tasks-transact-sql.md)) that was selected as a deadlock victim. It may be 0 (zero) in the case of an unresolved deadlock. A task that is rolling back cannot be chosen as a deadlock victim.<br /><br /> **executionstack**. Represents [!INCLUDE[tsql](../includes/tsql-md.md)] code that is being executed at the time the deadlock occurs.<br /><br /> **priority**. Represents deadlock priority. In certain cases, the [!INCLUDE[ssDEnoversion](../includes/ssdenoversion-md.md)] may opt to alter the deadlock priority for a short duration to achieve better concurrency.<br /><br /> **logused**. Log space used by the task.<br /><br /> **owner id**. The ID of the transaction that has control of the request.<br /><br /> **status**. State of the task. It is one of the following values:<br /><br /> >> **pending**. Waiting for a worker thread.<br /><br /> >> **runnable**. Ready to run but waiting for a quantum.<br /><br /> >> **running**. Currently running on the scheduler.<br /><br /> >> **suspended**. Execution is suspended.<br /><br /> >> **done**. Task has completed.<br /><br /> >> **spinloop**. Waiting for a spinlock to become free.<br /><br /> **waitresource**. The resource needed by the task.<br /><br /> **waittime**. Time in milliseconds waiting for the resource.<br /><br /> **schedulerid**. Scheduler associated with this task. See [sys.dm_os_schedulers (Transact-SQL)](../relational-databases/system-dynamic-management-views/sys-dm-os-schedulers-transact-sql.md).<br /><br /> **hostname**. The name of the workstation.<br /><br /> **isolationlevel**. The current transaction isolation level.<br /><br /> **Xactid**. The ID of the transaction that has control of the request.<br /><br /> **currentdb**. The ID of the database.<br /><br /> **lastbatchstarted**. The last time a client process started batch execution.<br /><br /> **lastbatchcompleted**. The last time a client process completed batch execution.<br /><br /> **clientoption1 and clientoption2**. Set options on this client connection. This is a bitmask that includes information about options usually controlled by SET statements such as SET NOCOUNT and SET XACTABORT.<br /><br /> **associatedObjectId**. Represents the HoBT (heap or B-tree) ID.|  
+|Identifying attributes|**SPID:<x\> ECID:<x\>.** Identifies the system process ID thread in cases of parallel processes. The entry `SPID:<x> ECID:0`, where <x\> is replaced by the SPID value, represents the main thread. The entry `SPID:<x> ECID:<y>`, where <x\> is replaced by the SPID value and <y\> is greater than 0, represents the subthreads for the same SPID.<br /><br /> **BatchID** (**sbid** for Trace Flag 1222). Identifies the batch from which code execution is requesting or holding a lock. When Multiple Active Result Sets (MARS) is disabled, the BatchID value is 0. When MARS is enabled, the value for active batches is 1 to *n*. If there are no active batches in the session, BatchID is 0.<br /><br /> **Mode**. Specifies the type of lock for a particular resource that is requested, granted, or waited on by a thread. Mode can be IS (Intent Shared), S (Shared), U (Update), IX (Intent Exclusive), SIX (Shared with Intent Exclusive), and X (Exclusive).<br /><br /> **Line #** (**line** for Trace Flag 1222). Lists the line number in the current batch of statements that was being executed when the deadlock occurred.<br /><br /> **Input Buf** (**inputbuf** for Trace Flag 1222). Lists all the statements in the current batch.|**Node**. Represents the entry number in the deadlock chain.<br /><br /> **Lists**. The lock owner can be part of these lists:<br /><br /> **Grant List**. Enumerates the current owners of the resource.<br /><br /> **Convert List**. Enumerates the current owners that are trying to convert their locks to a higher level.<br /><br /> **Wait List**. Enumerates current new lock requests for the resource.<br /><br /> **Statement Type**. Describes the type of DML statement (SELECT, INSERT, UPDATE, or DELETE) on which the threads have permissions.<br /><br /> **Victim Resource Owner**. Specifies the participating thread that [!INCLUDE[ssNoVersion](../includes/ssnoversion-md.md)] chooses as the victim to break the deadlock cycle. The chosen thread and all existing subthreads are terminated.<br /><br /> **Next Branch**. Represents the two or more subthreads from the same SPID that are involved in the deadlock cycle.|**deadlock victim**. Represents the physical memory address of the task (see [sys.dm_os_tasks (Transact-SQL)](../relational-databases/system-dynamic-management-views/sys-dm-os-tasks-transact-sql.md)) that was selected as a deadlock victim. It might be 0 (zero) in the case of an unresolved deadlock. A task that is rolling back cannot be chosen as a deadlock victim.<br /><br /> **executionstack**. Represents [!INCLUDE[tsql](../includes/tsql-md.md)] code that is being executed at the time the deadlock occurs.<br /><br /> **priority**. Represents deadlock priority. In certain cases, the [!INCLUDE[ssDEnoversion](../includes/ssdenoversion-md.md)] might opt to alter the deadlock priority for a short duration to achieve better concurrency.<br /><br /> **logused**. Log space used by the task.<br /><br /> **owner id**. The ID of the transaction that has control of the request.<br /><br /> **status**. State of the task. It is one of the following values:<br /><br /> >> **pending**. Waiting for a worker thread.<br /><br /> >> **runnable**. Ready to run but waiting for a quantum.<br /><br /> >> **running**. Currently running on the scheduler.<br /><br /> >> **suspended**. Execution is suspended.<br /><br /> >> **done**. Task has completed.<br /><br /> >> **spinloop**. Waiting for a spinlock to become free.<br /><br /> **waitresource**. The resource needed by the task.<br /><br /> **waittime**. Time in milliseconds waiting for the resource.<br /><br /> **schedulerid**. Scheduler associated with this task. See [sys.dm_os_schedulers (Transact-SQL)](../relational-databases/system-dynamic-management-views/sys-dm-os-schedulers-transact-sql.md).<br /><br /> **hostname**. The name of the workstation.<br /><br /> **isolationlevel**. The current transaction isolation level.<br /><br /> **Xactid**. The ID of the transaction that has control of the request.<br /><br /> **currentdb**. The ID of the database.<br /><br /> **lastbatchstarted**. The last time a client process started batch execution.<br /><br /> **lastbatchcompleted**. The last time a client process completed batch execution.<br /><br /> **clientoption1 and clientoption2**. Set options on this client connection. This is a bitmask that includes information about options usually controlled by SET statements such as SET NOCOUNT and SET XACTABORT.<br /><br /> **associatedObjectId**. Represents the HoBT (heap or B-tree) ID.|  
 |Resource attributes|**RID**. Identifies the single row within a table on which a lock is held or requested. RID is represented as RID: `db_id:file_id:page_no:row_no`. For example, `RID: 6:1:20789:0`.<br /><br /> **OBJECT**. Identifies the table on which a lock is held or requested. OBJECT is represented as OBJECT: `db_id:object_id`. For example, `TAB: 6:2009058193`.<br /><br /> **KEY**. Identifies the key range within an index on which a lock is held or requested. KEY is represented as KEY: `db_id:hobt_id` (*index key hash value*). For example, `KEY: 6:72057594057457664 (350007a4d329)`.<br /><br /> **PAG**. Identifies the page resource on which a lock is held or requested. PAG is represented as PAG: `db_id:file_id:page_no`. For example, `PAG: 6:1:20789`.<br /><br /> **EXT**. Identifies the extent structure. EXT is represented as EXT: `db_id:file_id:extent_no`. For example, `EXT: 6:1:9`.<br /><br /> **DB**. Identifies the database lock. **DB is represented in one of the following ways:**<br /><br /> DB: `db_id`<br /><br /> DB: `db_id[BULK-OP-DB]`, which identifies the database lock taken by the backup database.<br /><br /> DB: `db_id[BULK-OP-LOG]`, which identifies the lock taken by the backup log for that particular database.<br /><br /> **APP**. Identifies the lock taken by an application resource. APP is represented as APP: `lock_resource`. For example, `APP: Formf370f478`.<br /><br /> **METADATA**. Represents metadata resources involved in a deadlock. Because METADATA has many subresources, the value returned depends upon the subresource that has deadlocked. For example, `METADATA.USER_TYPE` returns `user_type_id = *integer_value*`. For more information about METADATA resources and subresources, see [sys.dm_tran_locks (Transact-SQL)](../relational-databases/system-dynamic-management-views/sys-dm-tran-locks-transact-sql.md).<br /><br /> **HOBT**. Represents a heap or B-tree involved in a deadlock.|None exclusive to this trace flag.|None exclusive to this trace flag.|  
   
 #### Trace Flag 1204 example
@@ -513,7 +513,7 @@ You can view the XML in the `Deadlock_XML` column inside SSMS, by selecting the
 
 **Applies to:** [!INCLUDE[ssazure-sqldb](../includes/ssazure-sqldb.md)]
 
-[Optimized locking](performance/optimized-locking.md) introduced a different method for locking mechanics that changes how deadlocks involving exclusive TID locks may be reported. Under each resource in the deadlock report's `<resource-list>`, each `<xactlock>` element reports the underlying resources and specific information for locks of each member of a deadlock. 
+[Optimized locking](performance/optimized-locking.md) introduced a different method for locking mechanics that changes how deadlocks involving exclusive TID locks might be reported. Under each resource in the deadlock report's `<resource-list>`, each `<xactlock>` element reports the underlying resources and specific information for locks of each member of a deadlock. 
 
 Consider the following example where optimized locking is enabled:
 
@@ -572,4 +572,4 @@ This scenario of competing `UPDATE` statements results in a deadlock. In this ca
 - [Lock:Deadlock Event Class](event-classes/lock-deadlock-event-class.md)
 - [SET DEADLOCK_PRIORITY (Transact-SQL)](../t-sql/statements/set-deadlock-priority-transact-sql.md)
 - [Analyze and prevent deadlocks in Azure SQL Database](/azure/azure-sql/database/analyze-prevent-deadlocks)
-- [Open, view, and print a deadlock file in SQL Server Management Studio (SSMS)](performance/open-view-and-print-a-deadlock-file-sql-server-management-studio.md)
+- [Open, view, and print a deadlock file in SQL Server Management Studio (SSMS)](performance/open-view-and-print-a-deadlock-file-sql-server-management-studio.md)
