PG_THREAD_WAIT_STATUS

PG_THREAD_WAIT_STATUS allows you to test the block waiting status about the backend thread and auxiliary thread of the current instance. For details about the columns, see Table 1.

**Table 1** PG_THREAD_WAIT_STATUS columns
Name	Type	Description
node_name	text	Current node name.
db_name	text	Database name.
thread_name	text	Thread name.
query_id	bigint	Query ID. It is equivalent to debug_query_id.
tid	bigint	Thread ID of the current thread.
sessionid	bigint	Current session ID.
lwtid	integer	Lightweight thread ID of the current thread.
psessionid	bigint	Parent session ID.
tlevel	integer	Level of the streaming thread.
smpid	integer	Concurrent thread ID.
wait_status	text	Waiting status of the current thread. For details about the waiting status, see Table 2.
wait_event	text	If wait_status is acquire lock, acquire lwlock, or wait io, this column describes the lock, lightweight lock, or I/O information. Otherwise, this column is empty.
locktag	text	Information about the lock that the current thread is waiting to obtain.
lockmode	text	Lock mode that the current thread is waiting to obtain. The values include table-level lock, row-level lock, and page-level lock modes.
block_sessionid	bigint	ID of the session that blocks the current thread from obtaining the lock.
global_sessionid	text	Global session ID.

Table 2 shows the waiting status in the wait_status column.

**Table 2** Waiting state list
Value	Description
none	Waiting for no event.
acquire lock	Waiting for locking until the locking succeeds or times out.
acquire lwlock	Waiting for a lightweight lock.
wait io	Waiting until the I/O is complete
wait cmd	Waiting for reading network communication packets to complete.
wait pooler get conn	Waiting for pooler to obtain connections.
wait pooler abort conn	Waiting for pooler to terminate connections.
wait pooler clean conn	Waiting for pooler to clear connections.
pooler create conn: [nodename], total N	Waiting for the pooler to set up a connection. The connection is being established with the node specified by nodename, and there are N connections waiting to be set up.
get conn	Obtaining the connection to other nodes.
set cmd: [nodename]	Waiting for running the SET, RESET, TRANSACTION BLOCK LEVEL PARA SET, or SESSION LEVEL PARA SET command on the connection. The statement is being executed on the node specified by nodename.
cancel query	Canceling the SQL statement that is being executed through the connection.
stop query	Stopping the query that is being executed through the connection.
wait node: [nodename](plevel), total N, [phase]	Waiting for receiving data from a connected node. The thread is waiting for data from the plevel thread of the node specified by nodename. The data of N connections is waiting to be returned. If phase is included, the possible phases are as follows: begin: The transaction is being started. commit: The transaction is being committed. rollback: The transaction is being rolled back.
wait transaction sync: xid	Waiting for synchronizing the transaction specified by xid.
wait wal sync	Waiting for the completion of WAL of synchronization from the specified LSN to the standby instance.
wait data sync	Waiting for the completion of data page synchronization to the standby instance.
wait data sync queue	Waiting for putting the data pages that are in the row-store into the synchronization queue.
flush data: [nodename](plevel), [phase]	Waiting for sending data to the plevel thread of the node specified by nodename. If phase is included, the possible phase is wait quota, indicating that the current communication flow is waiting for the quota value.
stream get conn: [nodename], total N	Waiting for connecting to the consumer object of the node specified by nodename when the stream flow is initialized. There are N consumers waiting to be connected.
wait producer ready: [nodename](plevel), total N	Waiting for each producer to be ready when the stream flow is initialized. The thread is waiting for the procedure of the plevel thread on the nodename node to be ready. There are N producers waiting to be ready.
synchronize quit	Waiting for the threads in the stream thread group to quit when the stream plan ends.
nodegroup destroy	Waiting for destroying the stream node group when the stream plan ends.
wait active statement	Waiting for job execution under resource and load control.
gtm connect	Waiting for connecting to GTM.
gtm get gxid	Waiting for obtaining xid from GTM.
gtm get snapshot	Waiting for obtaining transaction snapshots from GTM.
gtm begin trans	Waiting for GTM to start a transaction.
gtm commit trans	Waiting for GTM to commit a transaction.
gtm rollback trans	Waiting for GTM to roll back a transaction.
gtm start prepare trans	Waiting for GTM to start the prepare phase of a two-phase transaction.
gtm prepare trans	Waiting for GTM to complete the prepare phase of a two-phase transaction.
gtm open sequence	Waiting for GTM to open a sequence.
gtm close sequence	Waiting for GTM to close a sequence.
gtm create sequence	Waiting for GTM to create a sequence.
gtm alter sequence	Waiting for GTM to modify a sequence.
gtm get sequence val	Waiting for obtaining the next value of a sequence from GTM.
gtm set sequence val	Waiting for GTM to set a sequence value.
gtm drop sequence	Waiting for GTM to delete a sequence.
gtm rename sequence	Waiting for GTM to rename a sequence.
analyze: [relname], [phase]	The thread is running ANALYZE to the relname table. If phase is included, the possible phase is autovacuum, indicating that the database automatically enables the AutoVacuum thread to run ANALYZE.
vacuum: [relname], [phase]	The thread is running VACUUM to the relname table. If phase is included, the possible phase is autovacuum, indicating that the database automatically enables the AutoVacuum thread to run VACUUM.
vacuum full: [relname]	The thread is running VACUUM FULL to the relname table.
create index	Creating an index.
HashJoin - [ build hash \| write file ]	The HashJoin operator is being executed. In this phase, you need to pay attention to the execution time-consuming. build hash: The HashJoin operator is creating a hash table. write file: The HashJoin operator is writing data to disks.
HashAgg - [ build hash \| write file ]	The HashAgg operator is being executed. In this phase, you need to pay attention to the execution time-consuming. build hash: The HashAgg operator is creating a hash table. write file: The HashAgg operator is writing data to disks.
HashSetop - [build hash \| write file ]	The HashSetop operator is being executed. In this phase, you need to pay attention to the execution time-consuming. build hash: The HashSetop operator is creating a hash table. write file: The HashSetop operator is writing data to disks.
Sort \| Sort - [fetch tuple \| write file]	The Sort operator is used for sorting. fetch tuple indicates that the Sort operator is obtaining tuples, and write file indicates that the Sort operator is writing data to disks.
Material \| Material - write file	The Material operator is being executed. write file indicates that the Material operator is writing data to disks.
standby read recovery conflict	The read-only mode of the standby node conflicts with the log replay mode.
standby get snapshot	The standby node obtains the snapshot in read-only mode.
prune table	Waiting for a heap table to clear historical deleted data.
prune index	Waiting for an index to clear historical deleted data.
vacuum gpi	Waiting for a GPI index to clear historical deleted data.
gtm reset xmin	Waiting for GTM to reset the minimum transaction ID.
gtm get xmin	Waiting for obtaining the minimum transaction ID from GTM.
gtm get csn	Waiting for obtaining the CSN from GTM.
gtm start preprare trans	Waiting for the GTM to start a two-phase transaction.
gtm rename sequence	Waiting for the GTM to rename a sequence.
wait reserve td	Waiting for an Ustore transaction slot allocation.
wait td rollback	Waiting for an Ustore transaction slot to roll back transactions.
wait available td	Waiting for an available transaction slot for Ustore.
wait transaction rollback	Waiting for a transaction to roll back.
gtm set disaster cluster	Waiting for setting the DR cluster information on the GTM.
gtm get disaster cluster	Waiting for obtaining the DR cluster information from the GTM.
gtm del disaster cluster	Waiting for deleting the DR cluster information from the GTM.
gtm set consistency point	Waiting for setting the consistency point in GTM.
wait sync bgworkers	Waiting for an index subthread created in parallel to complete local scanning and sorting.
wait gs_sleep	Waiting for the server thread delay.
wait vacuum delay	Waiting for VACUUM delay.
wait seq scan	Execution time of seq scan.
wait index scan	Execution time of index scan.
wait checkpoint start	Start time of the checkpoint phase.
wait checkpoint done	End time of the checkpoint phase.
wait xact start command	Start time of xact.
wait xact commit command	Commit time of xact.
wait io control	Waiting for job execution under I/O control.
security audit write pipe	Waiting for an audit log to be written to the pipe.

If wait_status is acquire lwlock, acquire lock, or wait io, there is an event performing I/O operations or waiting for obtaining the corresponding lightweight lock or transaction lock.

Table 3 describes the corresponding wait events when wait_status is acquire lwlock. If wait_event is extension, the lightweight lock is dynamically allocated and is not monitored.

**Table 3** List of wait events corresponding to lightweight locks
wait_event	Description
ShmemIndexLock	Used to protect the primary index table, a hash table, in shared memory
OidGenLock	Used to prevent different threads from generating the same OID
XidGenLock	Used to prevent two transactions from obtaining the same XID
ProcArrayLock	Used to prevent concurrent access to or concurrent modification on the ProcArray shared array
SInvalReadLock	Used to prevent concurrent execution with invalid message deletion
SInvalWriteLock	Used to prevent concurrent execution with invalid message write and deletion
WALInsertLock	Used to prevent concurrent execution with WAL insertion
WALWriteLock	Used to prevent concurrent write from a WAL buffer to a disk
ControlFileLock	Used to prevent concurrent read/write or concurrent write/write on the pg_control file
CheckpointLock	Used to prevent multi-checkpoint concurrent execution
CLogControlLock	Used to prevent concurrent access to or concurrent modification on the Clog control data structure
SubtransControlLock	Used to prevent concurrent access to or concurrent modification on the subtransaction control data structure
MultiXactGenLock	Used to allocate a unique MultiXact ID in serial mode
MultiXactOffsetControlLock	Used to prevent concurrent read/write or concurrent write/write on pg_multixact/offset
MultiXactMemberControlLock	Used to prevent concurrent read/write or concurrent write/write on pg_multixact/members
RelCacheInitLock	Used to add a lock before any operations are performed on the init file when messages are invalid
CheckpointerCommLock	Used to send file flush requests to a checkpointer. The request structure needs to be inserted to a request queue in serial mode.
TwoPhaseStateLock	Used to prevent concurrent access to or modification on two-phase information sharing arrays
TablespaceCreateLock	Used to check whether a tablespace exists.
BtreeVacuumLock	Used to prevent VACUUM from clearing pages that are being used by B-tree indexes
AlterPortLock	Used to protect the CN's operation of changing the registered port number.
AutovacuumLock	Used to access the autovacuum worker array in serial mode
AutovacuumScheduleLock	Used to distribute tables requiring VACUUM in serial mode
AutoanalyzeLock	Used to obtain and release resources related to a task that allows for autoanalyze execution
SyncScanLock	Used to determine the start position of a relfilenode during heap scanning
NodeTableLock	Used to protect a shared structure that stores CN and DN node information.
PoolerLock	Used to prevent two threads from simultaneously obtaining the same connection from a connection pool
RelationMappingLock	Used to wait for the mapping file between system catalogs and storage locations to be updated
Async Ctl	Used to protect asynchronization buffers.
AsyncCtlLock	Used to prevent concurrent access to or concurrent modification on the sharing notification status
AsyncQueueLock	Used to prevent concurrent access to or concurrent modification on the sharing notification queue
SerializableXactHashLock	Used to prevent concurrent read/write or concurrent write/write on a sharing structure for serializable transactions
SerializableFinishedListLock	Used to prevent concurrent read/write or concurrent write/write on a shared linked list for completed serial transactions
SerializablePredicateLockListLock	Used to protect a linked list of serializable transactions that have locks
OldSerXidLock	Used to protect a structure that records serializable transactions that have conflicts
FileStatLock	Used to protect a data structure that stores statistics file information
SyncRepLock	Used to protect Xlog synchronization information during primary-standby replication
DataSyncRepLock	Used to protect data page synchronization information during primary-standby replication
MetaCacheSweepLock	Used to add a lock when metadata is cyclically washed out
ExtensionConnectorLibLock	Used to add a lock when a specific dynamic library is loaded or uninstalled in ODBC connection initialization scenarios
SearchServerLibLock	Used to add a lock on the file read operation when a specific dynamic library is initially loaded in GPU-accelerated scenarios
LsnXlogChkFileLock	Used to serially update the Xlog flush points for primary and standby servers recorded in a specific structure
GTMHostInfoLock	Used to prevent concurrent access to or concurrent modification on GTM host information
ReplicationSlotAllocationLock	Used to add a lock when a primary server allocates streaming replication slots during primary-standby replication
ReplicationSlotControlLock	Used to prevent concurrent update of replication slot status during primary-standby replication
ResourcePoolHashLock	Used to prevent concurrent access to or concurrent modification on a resource pool table, a hash table
OBSGetPathLock	Used to prevent concurrent read/write or concurrent write/write on an OBS path
JobShmemLock	Used to protect global variables in the shared memory that is periodically read during a scheduled task where MPP is compatible with Oracle
OBSRuntimeLock	Used to obtain environment variables, for example, GASSHOME
LLVMDumpIRLock	Used to export the assembly language for dynamically generating functions.
LLVMParseIRLock	Used to compile and parse a finished IR function from the IR file at the start position of a query.
CriticalCacheBuildLock	Used to load caches from a shared or local cache initialization file
WaitCountHashLock	Used to protect a shared structure in user statement counting scenarios
BufMappingLock	Used to protect operations on a table mapped to shared buffer
LockMgrLock	Used to protect a common lock structure
PredicateLockMgrLock	Used to protect a lock structure that has serializable transactions
OperatorRealTLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the operator level
OperatorHistLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the operator level
SessionRealTLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the query level
SessionHistLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the query level
CacheSlotMappingLock	Used to protect global CU cache information
BarrierLock	Used to ensure that only one thread is creating a barrier at a time
GPCCommitLock	Used to protect the addition of the global plan cache hash table.
GPCClearLock	Used to protect the clearing of the global plan cache hash table.
GPCTimelineLock	Used to protect the timeline check of the global plan cache hash table.
GPCMappingLock	Used to manage the global plan cache.
GPCPrepareMappingLock	Used to manage the global plan cache.
GPRCMappingLock	Used to manage the access and modification operations of the global cache hash table of autonomous transactions.
BufFreelistLock	Used to ensure the atomicity of free list operations in the shared buffer.
AddinShmemInitLock	Used to protect the initialization of the shared memory object.
wait active statement	Waiting for job execution under resource and load control.
wait memory	Waiting for obtaining the memory.
DnUsedSpaceHashLock	Used to update space usage information corresponding to a session.
InstanceRealTLock	Used to protect the update of the hash table that stores shared instance statistics.
IOStatLock	Used to concurrently maintain the hash table of resource management I/O statistics.
PldebugLock	Used to debug stored procedures and perform concurrent maintenance operations.
StartBlockMappingLock	Used by globalstat to obtain information such as startblockarray from pgstat.
GlobalSeqLock	Used to manage global sequence numbers.
MatviewSeqnoLock	Used to manage the cache of materialized views.
DataFileIdCacheLock	Used to manage the concurrent access and storage of hash table that stores data file descriptor in the shared memory.
GTMHostInfoLock	Used to protect the concurrent access and storage of shared GTM host information.
TwoPhaseStatePartLock	Used to protect the status information of two-phase transactions (in each partition).
WALBufMappingLock	Used to protect the mapping between WAL buffer page and LSN offset.
UndoZoneLock	Used to protect the concurrent access and storage of undo zone.
RollbackReqHashLock	Used to protect the concurrent access and storage of hash table that stores the rollback request in the shared memory.
UHeapStatLock	Used to protect the concurrent access and storage of Ustore statistics.
WALWritePaxosLock	Used to protect the concurrent sequence of WAL log written to the paxos replication component.
SyncPaxosLock	Used to protect the concurrent access and storage of paxos synchronization queue.
BackgroundWorkerLock	Used to protect the concurrent sequence of background workers.
HadrSwitchoverLock	Used to protect the concurrent sequence of DR switchover.
HashUidLock	Used to protect the concurrent sequence of UID allocation.
ParallelDecodeLock	Used to protect the concurrent sequence of parallel decoding.
XLogMaxCSNLock	Used to protect the maximum volume of CSNs that can be restored locally in DR mode.
DisasterCacheLock	Used to protect the concurrent access and storage of DR cache information in the shared memory.
MaxCSNArrayLock	Used to protect the restoration progress of standby node CSNs in each shard in the shared memory.
RepairBadBlockStatHashLock	Used to protect the concurrent access and storage of the hash table that stores damaged pages in the shared memory.
DropArchiveSlotLock	Used to protect the concurrent sequence of deleting the archive slot.
ProcXactMappingLock	Used to protect the concurrent access and storage of the hash table that stores the mapping information between transaction IDs and threads.
UndoPerZoneLock	Used to protect the concurrent access and storage of each information in undo zone.
UndoSpaceLock	Used to protect the concurrent access and storage of undo space.
SnapshotBlockLock	Used to control the concurrent sequence of snapshot-based backup and disk flushing.
DWSingleFlushFirstLock	Used to control the concurrent sequence of non-segment-pages and single-page doublewrite files.
DWSingleFlushSecondLock	Used to control the concurrent sequence of segment-pages and single-page doublewrite files.
DWSingleFlushSecondBufTagLock	Used to control the concurrent access and storage of metadata of segment-pages and single-page doublewrite files.
RestartPointQueueLock	Used to control the concurrent access and storage of restart point arrays on the standby node.
UnlinkRelHashTblLock	Used to protect the concurrent access and storage of the hash table that restores files to be deleted.
UnlinkRelForkHashTblLock	Used to protect the concurrent access and storage of the hash table that restores the fork files to be deleted.
WALFlushWait	Used to protect the concurrent sequence of log flushing.
WALConsensusWait	Used to protect the transaction commit or log replay which is performed only when the logs are consistent.
WALBufferInitWait	Used to protect the initialization and disk flushing sequence of WAL pages in the shared memory.
WALInitSegment	Used to protect the initialization sequence of WAL segment files.
SegmentHeadPartitionLock	Used to protect the partition lock of metadata in the segment-page header.
PgwrSyncQueueLock	Used to protect the concurrent access and storage of file queues to be flushed to disks.
BarrierHashTblLock	Used to protect the concurrent access and storage of barrier tables in the shared memory.
PageRepairHashTblLock	Used to protect the concurrent access and storage of the hash table that stores repaired pages.
FileRepairHashTblLock	Used to protect the concurrent access and storage of the hash table that stores repaired files.
BadBlockStatHashLock	Used to protect the concurrent access and storage of the hash table that stores damaged pages in the shared memory.
BufferIOLock	Used to protect the concurrent I/O for loading or evicting a single page in the shared buffer.
BufferContentLock	Used to protect the concurrent read and write operations on a single page in the shared buffer.
CUSlotListLock	Used to protect the concurrent access and storage of the slot linked list in the shared CU.
DataCacheLock	Used to protect the concurrent access and storage of the read-only cache in the shared CU.
MetaCacheLock	Used to protect the concurrent access and storage of the meta cache in the shared CU.
CBMParseXlogLock	Used to control the concurrent access and storage of CBM files.
CLogBufMappingLock	Used to control the concurrent access and storage of mapping in the shared clog page.
CLOG Ctl	Used to control the concurrent access and storage of each clog partition.
CSNBufMappingLock	Used to control the concurrent access and storage of mapping in the shared csnlog page.
CSNLOG Ctl	Used to control the concurrent access and storage of each csnlog partition.
DelayDDLLock	Used to control the concurrent sequence of DDL and delay backup function of the deletion.
DoubleWriteLock	Used to control the concurrent sequence of double write module.
DfsConnectorCacheLock	Used to control the concurrent access and storage of dfs connection cache.
DfsUserLoginLock	Used to control the concurrent sequence of dfs user login.
DfsSpaceCacheLock	Used to control the concurrent sequence of dfs space management cache.
PGPROCLock	Used to protect the concurrent access and storage of global shared thread array.
RelfilenodeReuseLock	Used to control the concurrent sequence of file name reuse.
ReplicationSlotLock	Used to protect the concurrent access and storage of logical replication slot.
LogicalReplicationSlotPersistentDataLock	Used to control the concurrent access and storage of logical replication slot persistence.
RowPageReplicationLock	Used to control the concurrent sequence of row-store page replication.
MultiXactOffset Ctl	Used to protect the concurrent access and storage of multixact offset document.
MultiXactMember Ctl	Used to protect the concurrent access and storage of multixact member document.
OldSerXid SLRU Ctl	Used to protect the concurrent access and storage of oldser transaction ID cache.
FullBuildXlogCopyStartPtrLock	Used to control the concurrent access and storage of the start point of full build request.
RcvWriteLock	Used to control the concurrent sequence of WAL receiver writer.
XlogRemoveSegLock	Used to control the concurrent access and storage of latest deleted WAL document.
CsnMinLock	Used to control the concurrent access and storage of CSN MIN
HypoIndexLock	Used to create, delete and reset the virtual index by the lightweight lock.
XGBoostLibLock	Used by DB4AI to call the XGBoost library.
InstrUserLockId	Used to protect the concurrent modification of the hash table that stores user login and logout records.
GsStackLock	Used to ensure that the gs_stack function is not concurrently invoked.
InstrStmtTrackCtlLock	Used to protect the concurrent access and storage of the hash table when full SQL statements are dynamically enabled.
CaptureViewFileHashLock	Used to protect the concurrent access and storage of the hash table when capturing the performance view.
UniqueSqlEvictLock	Used to protect the concurrent access and storage of the hash table when the unique SQL reclamation is enabled.
ASPMappingLock	Used to manage the concurrent access and storage of the ASP hash table.
AuditIndexFileLock	Used to protect concurrent read and write of index files in the audit log.
TDEKeyCacheLock	Used to control the concurrent read and write of cached data keys encrypted transparently.
SQLAdvisorLock	Used to manage the concurrent access and storage of recommended hash tables in distribution key management.
BlockchainVersionLock	Used to control the concurrent read and write of global block numbers in the ledger database.
GlobalPrevHashLock	Used to control the concurrent read and write of global verification hash tables in the ledger database.
LWTRANCHE_ACCOUNT_TABLE	Used to control the concurrent read and write of the hash table that stores the account locking status.

Table 4 describes the corresponding wait events when wait_status is wait io.

**Table 4** List of I/O wait events
wait_event	Description
BufFileRead	Reads data from a temporary file to a specified buffer.
BufFileWrite	Writes the content of a specified buffer to a temporary file.
ControlFileRead	Reads the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.
ControlFileSync	Flushes the pg_control file to a disk, mainly during database initialization.
ControlFileSyncUpdate	Flushes the pg_control file to a disk, mainly during database startup, checkpoint execution, and primary/standby verification.
ControlFileWrite	Writes the pg_control file, during database initialization.
ControlFileWriteUpdate	Updates the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.
CopyFileRead	Reads a file during file copying.
CopyFileWrite	Writes a file during file copying.
DataFileExtend	Writes a file during file name extension.
DataFileFlush	Flushes a table data file to a disk.
DataFileImmediateSync	Flushes a table data file to a disk immediately.
DataFilePrefetch	Reads a table data file asynchronously.
DataFileRead	Reads a table data file synchronously.
DataFileSync	Flushes table data file modifications to a disk.
DataFileTruncate	Truncates a table data file.
DataFileWrite	Writes a table data file.
LockFileAddToDataDirRead	Reads the postmaster.pid file.
LockFileAddToDataDirSync	Flushes the postmaster.pid file to a disk.
LockFileAddToDataDirWrite	Writes PID information into the postmaster.pid file.
LockFileCreateRead	Reads the LockFile file %s.lock.
LockFileCreateSync	Flushes the LockFile file %s.lock to a disk.
LockFileCreateWRITE	Writes PID information into the LockFile file %s.lock.
NgroupDestoryLock	Adds a lock to the concurrent modification of the Node Group hash table.
NGroupMappingLock	Adds a lock to the concurrent modification of a single bucket that protects the NodeGroup hash table.
RelationMapRead	Reads the mapping file between system catalogs and storage locations.
RelationMapSync	Flushes the mapping file between system catalogs and storage locations to a disk.
RelationMapWrite	Writes the mapping file between system catalogs and storage locations.
ReplicationSlotRead	Reads a streaming replication slot file during a restart.
ReplicationSlotRestoreSync	Flushes a streaming replication slot file to a disk during a restart.
ReplicationSlotSync	Flushes a temporary streaming replication slot file to a disk during checkpoint execution.
ReplicationSlotWrite	Writes a temporary streaming replication slot file during checkpoint execution.
SLRUFlushSync	Flushes the pg_clog, pg_subtrans, and pg_multixact files to a disk, mainly during checkpoint execution and database shutdown.
SLRURead	Reads the pg_clog, pg_subtrans, and pg_multixact files.
SLRUSync	Writes dirty pages into the pg_clog, pg_subtrans, and pg_multixact files, and flushes the files to a disk, mainly during checkpoint execution and database shutdown.
SLRUWrite	Writes the pg_clog, pg_subtrans, and pg_multixact files.
TimelineHistoryRead	Reads the timeline history file during database startup.
TimelineHistorySync	Flushes the timeline history file to a disk during database startup.
TimelineHistoryWrite	Writes to the timeline history file during database startup.
TwophaseFileRead	Reads the pg_twophase file, mainly during two-phase transaction commit and restoration.
TwophaseFileSync	Flushes the pg_twophase file to a disk, mainly during two-phase transaction commit and restoration.
TwophaseFileWrite	Writes the pg_twophase file, mainly during two-phase transaction commit and restoration.
WALBootstrapSync	Flushes an initialized WAL file to a disk during database initialization.
WALBootstrapWrite	Writes an initialized WAL file during database initialization.
WALCopyRead	Reads operation generated when an existing WAL file is read for replication after archiving and restoration.
WALCopySync	Flushes a replicated WAL file to a disk after archiving and restoration.
WALCopyWrite	Writes operation generated when an existing WAL file is read for replication after archiving and restoration.
WALInitSync	Flushes a newly initialized WAL file to a disk during log reclaiming or writing.
WALInitWrite	Initializes a newly created WAL file to 0 during log reclaiming or writing.
WALRead	Reads data from Xlogs during redo operations on two-phase files.
WALSyncMethodAssign	Flushes all open WAL files to a disk.
WALWrite	Writes a WAL file.
DoubleWriteFileRead	Waiting for reading the double-write file.
DoubleWriteFileSync	Waiting for flushing the double-write file to the disk.
DoubleWriteFileWrite	Waiting for writing the double-write file.
PredoProcessPending	Waiting for the replay of the remaining records processing in parallel.
PredoApply	Waiting for the replay of the application in parallel.
DisableConnectFileRead	Waiting for reading the lock segment file.
DisableConnectFileSync	Waiting for flushing lock segment files to the disk.
DisableConnectFileWrite	Waiting for writing the lock segment file.
BufHashTableSearch	Used to search the hash table in the shared buffer (page eviction may be triggered).
StrategyGetBuffer	Used to obtain pages from strategy buffer (page eviction may be triggered).
UndoFileExtend	Used to extend an undo file.
UndoFilePrefetch	Used to prefetch an undo file.
UndoFileRead	Used to read an undo file.
UndoFileWrite	Used to write an undo file.
UndoFileSync	Used to flash an undo file to disks.
UndoFileUnlink	Used to delete an undo file.
UndoMetaSync	Used to flash an undo metadata file to disks.
WALBufferAccess	Used to access WAL buffer (To ensure performance, only the number of access times is counted in the kernel code, and the access duration is not counted.).
WALBufferFull	Used to write WAL files when the WAL buffer is full.
DWSingleFlushGetPos	Used by a single-page doublewrite file to search for available location.
DWSingleFlushWrite	Used to flash a single-page doublewrite file to disks.
CkptWaitPageWriterFlush	Used to wait for page refreshing during full checkpoint execution.
CkptWaitPageWriterSync	Used to wait for the modified file to be synchronized to the disk before checkpointing.
CkptWaitCommitTransactionFinish	Used to wait until all transactions are committed before checkpointing.
MPFL_INIT	Used to initiate max_page_flush_lsn.
MPFL_READ	Used to read max_page_flush_lsn.
MPFL_WRITE	Used to write max_page_flush_lsn.
OBSList	Used to traverse an OBS directory.
OBSRead	Used to read an OBS object.
OBSWrite	Used to write an OBS object.
LOGCTRL_SLEEP	Waiting for the standby node to catch up with logs.
ShareStorageWalRead	Used to read log files from the shared disk.
ShareStorageWalWrite	Used to write log files to the shared disk.
ShareStorageCtlInfoRead	Used to read control information from the shared disk.
ShareStorageCtlInfoWrite	Used to write control information to the shared disk.
SegFileExtend	Used to extend segment-page files.
SegReadDisk	Used to read segment-page files.
SegWriteDisk	Used to write segment-page files.
SegSync	Used to flash segment-page files.
SegFileShrink	Used to collapse segment-page files.

Table 5 describes the corresponding wait events when wait_status is acquire lock.

**Table 5** List of wait events corresponding to transaction locks
wait_event	Description
relation	Adds a lock to a table.
extend	Adds a lock to a table being scaled out.
partition	Adds a lock to a partitioned table.
partition_seq	Adds a lock to a partition of a partitioned table.
page	Adds a lock to a table page.
tuple	Adds a lock to a tuple on a page.
transactionid	Adds a lock to a transaction ID.
virtualxid	Adds a lock to a virtual transaction ID.
object	Adds a lock to an object.
userlock	Adds a lock to a user.
advisory	Adds an advisory lock.
filenode	Used to lock the file name.
subtransactionid	Used to add a lock to a sub-transaction ID.
tuple_uid	Used to add a lock to the UID hidden field in the tuple header.