Help Center > > Developer Guide> Setting GUC Parameters> Write Ahead Logs> Settings

Settings

Updated at: Jul 15, 2020 GMT+08:00

synchronous_commit

Parameter description: Specifies the synchronization mode of the current transaction.

Type: USERSET

Value range: enumerated values

  • on indicates synchronization logs of a standby server are flushed to disks.
  • off indicates asynchronous commit.
  • local indicates local commit.
  • remote_write indicates synchronization logs of a standby server are written to disks.
  • remote_receive indicates synchronization logs of a standby server are required to receive data.

Default value: on

commit_delay

Parameter description: Specifies the duration of committed data be stored in the WAL buffer.

Type: USERSET

Value range: an integer, ranging from 0 to 100000 (unit: μs). 0 indicates no delay.

Default value: 0

  • When this parameter is set to a value other than 0, the committed transaction is stored in the WAL buffer instead of being written to the WAL immediately. Then, the WALwriter process flushes the buffer out to disks periodically.
  • If system load is high, other transactions are probably ready to be committed within the delay. If no transactions are waiting to be submitted, the delay is a waste of time.

commit_siblings

Parameter description: Specifies a limit on the number of ongoing transactions. If the number of ongoing transactions is greater than the limit, a new transaction will wait for the period of time specified by commit_delay before it is submitted. If the number of ongoing transactions is less than the limit, the new transaction is immediately written into a WAL.

Type: USERSET

Value range: an integer ranging from 0 to 1000

Default value: 5

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