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Table 3 List of wait events corresponding to I/Os

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, mainly 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 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 Read 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.
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 stream replication slot file during a restart.
ReplicationSlotRestoreSync Flushes a stream replication slot file to a disk during a restart.
ReplicationSlotSync Flushes a temporary stream replication slot file to a disk during checkpoint execution.
ReplicationSlotWrite Writes a temporary stream 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 Read 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 Write 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.
WALBufferAccess WAL Buffer access (for performance reasons, only the number of accesses are counted in the kernel code, and the access time is not counted).
WALBufferFull When the WAL Buffer is full, write wal file related processing.
DoubleWriteFileRead Doublewrites and reads a file.
DoubleWriteFileSync Doublewrites a file and forcibly flushes files to disks.
DoubleWriteFileWrite Doublewrites a file and writes a file.
PredoProcessPending Waits for the playback of other records to complete during parallel log playback.
PredoApply Waits for other threads to play back logs to the LSN of the current thread during parallel log playback.
DisableConnectFileRead Reads the HA lock fragment logic file.
DisableConnectFileSync Forcibly flushes the HA lock fragment logic file to disks.
DisableConnectFileWrite Writes the HA lock fragment logic file.
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