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.