Help Center/ GaussDB/ Distributed_8.x/ Schemas/ DBE_PERF Schema/ Wait Event/ WAIT_EVENT_INFO

Updated on 2024-06-03 GMT+08:00

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WAIT_EVENT_INFO

WAIT_EVENT_INFO displays the details about wait events, as described in Table 1 and Table 2.

**Table 1** WAIT_EVENT_INFO columns
Name	Type	Description
module	text	Name of the module an event belongs to.
type	text	Event type.
event	text	Event name.

**Table 2** Wait event information list
Module Category	Event Category	Event	Description
Lock	Wait event	acquire lock	Waits for locking until the locking succeeds or times out.
SharedMemory	LWLock event	ShmemIndexLock	Protects the primary index table, a hash table, in shared memory.
Shared buffer	LWLock event	BufMappingLock	Protects operations on a shared-buffer mapping table.
Lmgr	LWLock event	LockMgrLock	Protects the information about a common lock structure.
LWLock	Wait event	acquire lwlock	Waiting for a lightweight lock.
I/O	Wait event	wait io	Waiting for I/O completion.
COMM	Wait event	wait cmd	Waiting for reading network communication packets to complete.
COMM	Wait event	wait pooler get conn	Waiting for pooler to obtain connections.
COMM	Wait event	wait pooler abort conn	Waiting for pooler to terminate connections.
COMM	Wait event	wait pooler clean conn	Waiting for pooler to clear connections.
COMM	Wait event	get conn	Obtaining the connection to other nodes.
COMM	Wait event	set cmd	Waiting for running the SET, RESET, or TRANSACTION BLOCK LEVEL statement on the connection.
COMM	Wait event	cancel query	Canceling the SQL statement that is being executed through the connection.
COMM	Wait event	stop query	Stopping the query that is being executed through the connection.
COMM	Wait event	wait node	Waiting for receiving data through the connection to an instance.
COMM	Wait event	flush data	Waiting for sending data to other nodes in the network.
COMM	Wait event	stream get conn	Waits for establishing connections to consumer nodes when the stream flow is initialized.
COMM	Wait event	wait producer ready	Waits for every producer to get ready when the stream flow is initialized.
Stream	Wait event	synchronize quit	Waits for the threads in the stream thread group to quit when the stream plan ends.
Stream	Wait event	wait stream group destroy	Waits for destroying the stream node group when the stream plan ends.
Transaction	Wait event	wait transaction sync	Waiting for transaction synchronization.
Transaction	Wait event	wait data sync	Waiting for the completion of data page synchronization to the standby instance.
Transaction	Wait event	wait data sync queue	Waiting for putting the data pages that are in the row-store into the synchronization queue.
Transaction	LWLock event	OidGenLock	Prevents different threads from generating the same OID.
Transaction	LWLock event	XidGenLock	Prevents two transactions from obtaining the same transaction ID.
Transaction	LWLock event	ProcArrayLock	Prevents concurrent access to or concurrent modification on ProcArray shared arrays.
Transaction	LWLock event	SubtransControlLock	Used to prevent concurrent access to or concurrent modification on the subtransaction control data structure.
Transaction	LWLock event	MultiXactGenLock	Used to allocate a unique MultiXact ID in serial mode.
Transaction	LWLock event	TwoPhaseStateLock	Used to prevent concurrent access to or modification on two-phase information sharing arrays.
Transaction	LWLock event	SerializableXactHashLock	Used to prevent concurrent read/write or concurrent write/write on a sharing structure for serializable transactions.
Transaction	LWLock event	SerializableFinishedListLock	Used to prevent concurrent read/write or concurrent write/write on a shared linked list for completed serial transactions.
Transaction	LWLock event	SerializablePredicateLockListLock	Used to protect a linked list of serializable transactions that have locks.
Transaction	LWLock event	PredicateLockMgrLock	Used to protect the information about a lock structure that has serializable transactions.
Transaction	LWLock event	OldSerXid SLRU lwlock	Used to protect SLRU buffers of old transaction IDs.
Transaction	LWLock event	OldSerXidLock	Used to protect a structure that records serializable transactions that have conflicts.
Transaction	Lock event	transactionid	Adds a lock to a transaction ID.
Transaction	Lock event	virtualxid	Adds a lock to a virtual transaction ID.
Checkpoint	LWLock event	CheckpointLock	Used to prevent multi-checkpoint concurrent execution.
Checkpoint	LWLock event	CheckpointerCommLock	Used to send file flush requests to a checkpointer. The request structure needs to be inserted to a request queue in serial mode.
Analyze	LWLock event	AutoanalyzeLock	Used to obtain and release resources related to a task that allows for autoanalyze execution.
Vacuum	LWLock event	BtreeVacuumLock	Used to prevent VACUUM from clearing pages that are being used by B-tree indexes.
Vacuum	LWLock event	AutovacuumLock	Used to access the autovacuum worker array in serial mode.
Vacuum	LWLock event	AutovacuumScheduleLock	Used to distribute tables requiring VACUUM in serial mode.
Auto vacuum	LWLock event	AutovacuumLock	Protects the autovacuum shared memory structure.
Auto vacuum	LWLock event	AutovacuumScheduleLock	Used to protect the information about autovacuum workers.
Auto analyze	LWLock event	AutoanalyzeLock	Used to protect the autoAnalyzeFreeProcess variable and ensure that no more than 10 autoanalyze threads are running at the same time.
WAL	Wait event	wait wal sync	Waiting for the completion of WAL of synchronization from the specified LSN to the standby instance.
WAL	I/O event	WALBootstrapSync	Flushes an initialized WAL file to a disk during database initialization.
WAL	I/O event	WALBootstrapWrite	Writes an initialized WAL file during database initialization.
WAL	I/O event	WALCopyRead	Read operation generated when an existing WAL file is read for replication after archiving and restoration.
WAL	I/O event	WALCopySync	Flushes a replicated WAL file to a disk after archiving and restoration.
WAL	I/O event	WALCopyWrite	Write operation generated when an existing WAL file is read for replication after archiving and restoration.
WAL	I/O event	WALInitSync	Flushes a newly initialized WAL file to a disk during log reclaiming or writing.
WAL	I/O event	WALInitWrite	Initializes a newly created WAL file to 0 during log reclaiming or writing.
WAL	I/O event	WALRead	Reads data from Xlogs during redo operations on two-phase files.
WAL	I/O event	WALSyncMethodAssign	Flushes all open WAL files to a disk.
WAL	I/O event	WALWrite	Writes a WAL file.
WAL	I/O event	LOGCTRL_SLEEP	Collects statistics on the number of stream control times and the sleep time of log stream control.
WAL	LWLock event	RcvWriteLock	Used to prevent concurrent call of WalDataRcvWrite.
WAL	LWLock event	WALBufMappingLock	An exclusive (X) lock needs to be added when the next page of an Xlog buffer is initialized.
WAL	LWLock event	WALInsertLock	Used to prevent multiple programs from writing data to the same Xlog buffer at the same time.
WAL	LWLock event	WALWriteLock	Used to prevent concurrent WAL write.
Relation	LWLock event	SInvalReadLock	Used to prevent concurrent execution with invalid message deletion.
Relation	LWLock event	SinvalWriteLock	Used to prevent concurrent execution with invalid message write and deletion.
Relation	LWLock event	RelCacheInitLock	Used to add a lock before any operations are performed on the init file when messages are invalid.
Relation	LWLock event	TablespaceCreateLock	Used to check whether a tablespace already exists.
Relation	LWLock event	RelfilenodeReuseLock	Used to prevent the link to a reused column attribute file from being canceled by mistake.
Relation	Lock event	relation	Adds a lock to a table.
Relation	Lock event	extend	Adds a lock to a table being scaled out.
Relation	Lock event	partition	Adds a lock to a partitioned table.
Relation	Lock event	partition_seq	Adds a lock to a partition of a partitioned table.
WLM	Wait event	wait active statement	Waits for active statements.
WLM	Wait event	wait memory	Waits for free memory.
DDL/DCL	Wait event	create index	Waits for the completion of index creation.
DDL/DCL	Wait event	analyze	Waits for analysis completion.
DDL/DCL	Wait event	vacuum	Waits for the completion of the VACUUM operation.
DDL/DCL	LWLock event	DelayDDLLock	Used to prevent concurrent DDL operations.
DDL/DCL	Wait event	vacuum full	Waits for the completion of the VACUUM FULL operation.
Executor	Wait event	Sort	Waits for the completion of tuple sorting.
Executor	Wait event	Sort - write file	Writes sorted data to a file temporarily since the memory is limited during merge sort.
Executor	Wait event	Material	Waits for tuple materialization.
Executor	Wait event	Material - write file	Waits for writing a materialized tuple to a file.
Executor	Wait event	HashJoin - build hash	Waits until a hash table is created when a hash join is executed.
Executor	Wait event	HashJoin - write file	Waits for writing the hash result of a tuple to a disk when a hash join is executed.
Executor	Wait event	HashAgg - build hash	Waits until a hash table is created when a hash aggregate is executed.
Executor	Wait event	HashAgg - write file	Waits for writing the hash result of a tuple to a disk when a hash aggregate is executed.
Executor	Wait event	HashSetop - build hash	Waits until a hash table is created when an OP operation is performed using the hash algorithm.
Executor	Wait event	HashSetop - write file	Waits for writing the hash result of a tuple to a disk when an OP operation is performed using the hash algorithm.
Executor	Wait event	wait sync consumer next step	Waits for the stream consumer to perform the next step.
Executor	Wait event	wait sync producer next step	Waits for the stream producer to perform the next step.
GTM	Wait event	gtm connect	Waits for connecting to GTM.
GTM	Wait event	gtm reset xmin	Waits for GTM to reset the minimum transaction ID.
GTM	Wait event	gtm get xmin	Waits for obtaining the minimum transaction ID from GTM.
GTM	Wait event	gtm get gxid	Waits for obtaining the global transaction ID from GTM during transaction startup.
GTM	Wait event	gtm get csn	Waits for obtaining the CSN from GTM during transaction startup.
GTM	Wait event	gtm get snapshot	Waits for obtaining snapshots from GTM during transaction startup.
GTM	Wait event	gtm begin trans	Waits for GTM to start a transaction.
GTM	Wait event	gtm commit trans	Waits for GTM to commit a transaction.
GTM	Wait event	gtm rollback trans	Waits for GTM to roll back transactions.
GTM	Wait event	gtm start preprare trans	Waits for GTM to complete the first phase during two-phase commit.
GTM	Wait event	gtm prepare trans	Waits for GTM to complete the second phase during two-phase commit.
GTM	Wait event	gtm open sequence	Waits for GTM to create a sequence.
GTM	Wait event	gtm close sequence	Waits for GTM to complete the ALTER SEQUENCE operation.
GTM	Wait event	gtm set sequence val	Waits for GTM to set a sequence value.
GTM	Wait event	gtm drop sequence	Waits for GTM to delete a sequence.
GTM	Wait event	gtm rename sequence	Waits for GTM to rename a sequence.
GTM	LWLock event	GTMHostInfoLock	Used to protect GTM information.
Temp File	I/O event	BufFileRead	Reads data from a temporary file to a specified buffer.
Temp File	I/O event	BufFileWrite	Writes the content of a specified buffer to a temporary file.
Pg_control	I/O event	ControlFileRead	Reads the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.
Pg_control	I/O event	ControlFileSync	Flushes the pg_control file to a disk, mainly during database initialization.
Pg_control	I/O event	ControlFileSyncUpdate	Flushes the pg_control file to a disk, mainly during database startup, checkpoint execution, and primary/standby verification.
Pg_control	I/O event	ControlFileWrite	Writes the pg_control file, mainly during database initialization.
Pg_control	I/O event	ControlFileWriteUpdate	Updates the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.
Pg_control	LWLock event	ControlFileLock	Used to prevent concurrent read/write or concurrent write/write on the pg_control file.
File operation	I/O event	CopyFileRead	Reads a file during file copying.
File operation	I/O event	CopyFileWrite	Writes a file during file copying.
File operation	I/O event	DataFileExtend	Writes a file during file name extension.
Table data file	I/O event	DataFileImmediateSync	Flushes a table data file to a disk immediately.
Table data file	I/O event	DataFilePrefetch	Reads a table data file asynchronously.
Table data file	I/O event	DataFileRead	Reads a table data file synchronously.
Table data file	I/O event	DataFileSync	Synchronizes a table data file to a disk.
Table data file	I/O event	DataFileTruncate	Truncates a table data file.
Table data file	I/O event	DataFileWrite	Writes a table data file.
Table data file	LWLock event	SyncScanLock	Used to determine the start position of a relfilenode during heap scanning
Table data file	LWLock event	RelationMappingLock	Used to wait for the mapping file between system catalogs and storage locations to be updated.
metadata	LWLock event	MetaCacheSweepLock	Used to add a lock when metadata is cyclically washed out.
postmaster.pid	I/O event	LockFileAddToDataDirRead	Reads the postmaster.pid file.
postmaster.pid	I/O event	LockFileAddToDataDirSync	Flushes the postmaster.pid file to a disk.
postmaster.pid	I/O event	LockFileAddToDataDirWrite	Writes PID information into the postmaster.pid file.
Pid File	I/O event	LockFileCreateRead	Reads the LockFile file %s.lock.
Pid File	I/O event	LockFileCreateSync	Flushes the LockFile file %s.lock to a disk.
Pid File	I/O event	LockFileCreateWRITE	Writes PID information into the LockFile file %s.lock.
System catalog mapping file	I/O event	RelationMapRead	Reads the mapping file between system catalogs and storage locations.
System catalog mapping file	I/O event	RelationMapSync	Flushes the mapping file between system catalogs and storage locations to a disk.
System catalog mapping file	I/O event	RelationMapWrite	Writes the mapping file between system catalogs and storage locations.
Streaming replication	I/O event	ReplicationSlotRead	Reads a streaming replication slot file This operation is performed during a restart.
Streaming replication	I/O event	ReplicationSlotRestoreSync	Flushes a streaming replication slot file to a disk.
Streaming replication	I/O event	ReplicationSlotSync	Flushes a temporary streaming replication slot file to a disk during checkpoint execution.
Streaming replication	I/O event	ReplicationSlotWrite	Writes a temporary streaming replication slot file during checkpoint execution.
Streaming replication	LWLock event	ReplicationSlotAllocationLock	Used to allocate a replication slot.
Streaming replication	LWLock event	ReplicationSlotControlLock	Used to detect replication slot name conflicts and identify replication slots that can be allocated.
Clog	I/O event	SLRUFlushSync	Flushes the pg_clog file to a disk, mainly during checkpoint execution and database shutdown.
Clog	I/O event	SLRURead	Reads the pg_clog file.
Clog	I/O event	SLRUSync	Writes dirty pages into the pg_clog file, and flushes the file to a disk, mainly during checkpoint execution and database shutdown.
Clog	I/O event	SLRUWrite	Writes the pg_clog file.
Clog	LWLock event	CLogControlLock	Used to prevent concurrent access to or concurrent modification on the Clog control data structure.
Clog	LWLock event	MultiXactOffsetControlLock	Used to prevent concurrent read/write or concurrent write/write on pg_multixact/offset.
Clog	LWLock event	MultiXactMemberControlLock	Used to prevent concurrent read/write or concurrent write/write on pg_multixact/members.
timelinehistory	I/O event	TimelineHistoryRead	Reads the timelinehistory file, during database startup.
timelinehistory	I/O event	TimelineHistorySync	Flushes the timelinehistory file to a disk, during database startup.
timelinehistory	I/O event	TimelineHistoryWrite	Writes the timelinehistory file.
pg_twophase	I/O event	TwophaseFileRead	Reads the pg_twophase file, mainly during two-phase transaction commit and restoration.
pg_twophase	I/O event	TwophaseFileSync	Flushes the pg_twophase file to a disk, mainly during two-phase transaction commit and restoration.
pg_twophase	I/O event	TwophaseFileWrite	Writes the pg_twophase file, mainly during two-phase transaction commit and restoration.
Cluster	LWLock event	NodeTableLock	Used to protect a shared structure that stores CNs and DNs information.
Concurrency	LWLock event	PoolerLock	Used to prevent two threads from simultaneously obtaining the same connection from a connection pool.
Concurrency	LWLock event	AsyncCtlLock	Used to prevent concurrent access to or concurrent modification on the sharing notification status.
Concurrency	LWLock event	AsyncQueueLock	Used to prevent concurrent access to or concurrent modification on the sharing notification queue.
Double write	I/O event	DoubleWriteFileWrite	Writes pages to a doublewrite file during the doublewrite process.
Double write	I/O event	DoubleWriteFileRead	Reads a doublewrite file during restoration for a halfwrite.
Statistics file	LWLock event	FileStatLock	Used to protect a data structure that stores statistics file information.
Master-slave replication	LWLock event	SyncRepLock	Used to protect Xlog synchronization information during primary/standby replication.
Master-slave replication	LWLock event	ReplicationSlotAllocationLock	Used to add a lock when a primary server allocates streaming replication slots during primary/standby replication.
Master-slave replication	LWLock event	ReplicationSlotControlLock	Used to prevent concurrent update of streaming replication slot status during primary/standby replication.
Master-slave replication	LWLock event	LsnXlogChkFileLock	Used to serially update the Xlog flush points for primary and standby servers recorded in a specific structure.
Master-slave replication	LWLock event	DataSyncRepLock	Used to protect data page synchronization information during primary/standby replication.
Speed up the cluster	LWLock event	SearchServerLibLock	Used to add a lock on the file read operation when a specific dynamic library is initially loaded in GPU-accelerated scenarios.
Resource manage	LWLock event	ResourcePoolHashLock	Used to prevent concurrent access to or concurrent modification on a resource pool table, a hash table.
OBS	LWLock event	OBSGetPathLock	Used to prevent concurrent read/write or concurrent write/write on an OBS path.
OBS	LWLock event	OBSRuntimeLock	Used to obtain environment variables, for example, GASSHOME.
LLVM	LWLock event	LLVMDumpIRLock	Used to export the assembly language for dynamically generating functions.
LLVM	LWLock event	LLVMParseIRLock	Used to compile and parse a finished IR function from the IR file at the start position of a query.
MPP is compatible with ORACLE scheduled task function	LWLock event	JobShmemLock	Used to protect global variables in the shared memory that is periodically read during a scheduled task where MPP is compatible with Oracle.
Operator history information statistics	LWLock event	OperatorRealTLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the operator level.
Operator history information statistics	LWLock event	OperatorHistLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the operator level.
query history information statistics	LWLock event	SessionRealTLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the query level.
query history information statistics	LWLock event	SessionHistLock	Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the query level.
query history information statistics	LWLock event	WaitCountHashLock	Used to protect a shared structure in user statement counting scenarios.
barrier	LWLock event	BarrierLock	Used to ensure that only one thread is creating a barrier at a time.
CSN	LWLock event	CSNBufMappingLock	Used to protect CSN pages.
instrumentation	LWLock event	UniqueSQLMappingLock	Used to protect a unique SQL hash table.
instrumentation	LWLock event	InstrUserLock	Used to protect a user hash table.
instrumentation	LWLock event	PercentileLock	Used to protect global percentile buffers.
instrumentation	LWLock event	InstrWorkloadLock	Used to protect a workload transaction hash table.
Pgproc	LWLock event	Pgproc lwlock	Used to protect the PGPROC structure.
Async buffer	LWLock event	AsyncCtlLock	Used to protect asynchronization buffers.
MultiXact	LWLock event	MultiXactOffset lwlock	Used to protect SLRU buffers of a MultiXact offset.
MultiXact	LWLock event	MultiXactMemberlwlock	Used to protect SLRU buffer of a MultiXact member.
CBM	LWLock event	CBMParseXlogLock	Used to protect the lock used when CBM parses Xlogs.
BadBlock	LWLock event	BadBlockStatHashLock	Used to protect the hash table global_bad_block_stat.
Page	Lock event	page	Adds a lock to a table page.
Tuple	Lock event	tuple	Adds a lock to a tuple on a page.
object	Lock event	object	Adds a lock to an object.
user	Lock event	userlock	Adds a lock to a user.
advisor	Lock event	advisory	Adds an advisory lock.
ODBC	LWLock event	ExtensionConnectorLibLock	Adds a lock when a specific dynamic library is loaded or uninstalled in ODBC connection initialization scenarios.
COMM	Wait event	Accept client conn - Total Time	(After the GaussDB receives a connection request from a client) Total duration from the time when a connection is established to the time when the connection is successful.
COMM	Wait event	Accept client conn - ThrdPool - add epoll	(After the GaussDB receives a connection request from a client) Duration from the time when a connection is established to the time when the thread pool adds the session handle to the epoll in thread pool mode.
COMM	Wait event	Accept client conn - ThrdPool - wait worker	(After the GaussDB receives a connection request from a client) Duration from the time when the thread pool adds the session handle to the epoll to the time when the working thread pool starts to work in thread pool mode.
COMM	Wait event	Accept client conn - ThrdPool - init session	(After the GaussDB receives a connection request from a client) Duration from the time when the working thread pool starts to work to the time the session initialization ends in thread pool mode.
COMM	Wait event	Accept client conn - Worker - init proc	(After the GaussDB receives a connection request from a client) Duration from the time when a connection is established to the time when the thread initialization ends in non-thread pool mode.
COMM	Wait event	Accept client conn - Worker - init session	(After the GaussDB receives a connection request from a client) Duration from the time when the thread initialization ends to the time when the session initialization ends in non-thread pool mode.