• Data Warehouse Service

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  1. Help Center
  2. Data Warehouse Service
  3. Developer Guide
  4. Setting Configuration Parameters
  5. Appendix B: GUC Parameter Description
  6. Write Ahead Log
  7. Configuration

Configuration

synchronous_commit

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

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

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 that the standby server receives logs.

Default value: on

commit_delay

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

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

  • When this parameter is set to a non-zero value, 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.

Value range: an integer ranging from 0 to 100000 (ms)

Default value: 0 indicating no delay

commit_siblings

Parameter description: specifies a threshold on the number of concurrent open transactions. If the number of concurrent open transactions is greater than the value of this parameter, a transaction that initiates a commit request will wait for a period of time specified by commit_delay. Otherwise, this transaction is written into a WAL immediately.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: an integer ranging from 0 to 1000

Default value: 5