Postgres Plus Advanced Server Oracle Compatibility Developer's Guide : 11.8 Event Descriptions

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Postgres Plus Advanced Server Oracle Compatibility Developer's Guide

 

11.8 Event Descriptions

Event Name

Description

add in shmem lock acquire

Obsolete/unused

bgwriter communication lock acquire

The bgwriter (background writer) process has waited for the short-term lock that synchronizes messages between the bgwriter and a backend process.

btree vacuum lock acquire

The server has waited for the short-term lock that synchronizes access to the next available vacuum cycle ID.

buffer free list lock acquire

The server has waited for the short-term lock that synchronizes access to the list of free buffers (in shared memory).

checkpoint lock acquire:

A server process has waited for the short-term lock that prevents simultaneous checkpoints.

checkpoint start lock acquire

The server has waited for the short-term lock that synchronizes access to the bgwriter checkpoint schedule.

clog control lock acquire

The server has waited for the short-term lock that synchronizes access to the commit log.

control file lock acquire

The server has waited for the short-term lock that synchronizes write access to the control file (this should usually be a low number).

db file extend

A server process has waited for the operating system while adding a new page to the end of a file.

db file read

A server process has waited for the completion of a read (from disk).

db file write

A server process has waited for the completion of a write (to disk).

db file sync

A server process has waited for the operating system to flush all changes to disk.

first buf mapping lock acquire

The server has waited for a short-term lock that synchronizes access to the shared-buffer mapping table.

freespace lock acquire

The server has waited for the short-term lock that synchronizes access to the freespace map.

Infinite Cache read

The server has waited for an Infinite Cache read request.

Infinite Cache write

The server has waited for an Infinite Cache write request.

lwlock acquire

The server has waited for a short-term lock that has not been described elsewhere in this section.

multi xact gen lock acquire

The server has waited for the short-term lock that synchronizes access to the next available multi-transaction ID (when a SELECT...FOR SHARE statement executes).

multi xact member lock acquire

The server has waited for the short-term lock that synchronizes access to the multi-transaction member file (when a SELECT...FOR SHARE statement executes).

multi xact offset lock acquire

The server has waited for the short-term lock that synchronizes access to the multi-transaction offset file (when a SELECT...FOR SHARE statement executes).

oid gen lock acquire

The server has waited for the short-term lock that synchronizes access to the next available OID (object ID).

query plan

The server has computed the execution plan for a SQL statement.

rel cache init lock acquire

The server has waited for the short-term lock that prevents simultaneous relation-cache loads/unloads.

shmem index lock acquire

The server has waited for the short-term lock that synchronizes access to the shared-memory map.

sinval lock acquire

The server has waited for the short-term lock that synchronizes access to the cache invalidation state.

sql parse

The server has parsed a SQL statement.

subtrans control lock acquire

The server has waited for the short-term lock that synchronizes access to the subtransaction log.

tablespace create lock acquire

The server has waited for the short-term lock that prevents simultaneous CREATE TABLESPACE or DROP TABLESPACE commands.

two phase state lock acquire

The server has waited for the short-term lock that synchronizes access to the list of prepared transactions.

wal insert lock acquire

The server has waited for the short-term lock that synchronizes write access to the write-ahead log. A high number may indicate that WAL buffers are sized too small.

wal write lock acquire

The server has waited for the short-term lock that synchronizes write-ahead log flushes.

wal file sync

The server has waited for the write-ahead log to sync to disk (related to the wal_sync_method parameter which, by default, is 'fsync' - better performance can be gained by changing this parameter to open_sync).

wal flush

The server has waited for the write-ahead log to flush to disk.

wal write

The server has waited for a write to the write-ahead log buffer (expect this value to be high).

xid gen lock acquire

The server has waited for the short-term lock that synchronizes access to the next available transaction ID.

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