Help Center/ GaussDB(DWS)/ Developer Guide/ Standard data warehouse (8.1.3.x)/ GUC Parameters of the GaussDB(DWS) Database/ Cluster Transaction Parameters
Updated on 2024-11-05 GMT+08:00
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Cluster Transaction Parameters

This section describes the settings and value ranges of cluster transaction parameters.

transaction_isolation

Parameter description: Specifies the isolation level of the current transaction.

Type: USERSET

Value range:

  • READ COMMITTED: Only committed data is read. This is the default.
  • READ UNCOMMITTED: GaussDB(DWS) does not support READ UNCOMMITTED. If READ UNCOMMITTED is set, READ COMMITTED is executed instead.
  • REPEATABLE READ: Only the data committed before transaction start is read. Uncommitted data or data committed in other concurrent transactions cannot be read.
  • SERIALIZABLE: GaussDB(DWS) does not support SERIALIZABLE. If SERIALIZABLE is set, REPEATABLE READ is executed instead.

Default value: READ COMMITTED

transaction_read_only

Parameter description: Specifies that the current transaction is a read-only transaction.

Type: USERSET

Value range: Boolean

  • on indicates that the current transaction is a read-only transaction.
  • off indicates that the current transaction can be a read/write transaction.

Default value: off for CNs and on for DNs

xc_maintenance_mode

Parameter description: Specifies whether the system is in maintenance mode.

Type: SUSET

Value range: Boolean

  • on indicates that maintenance mode is enabled.
  • off indicates that the maintenance mode is disabled.

Default value: off

Enable the maintenance mode with caution to avoid cluster data inconsistencies.

allow_concurrent_tuple_update

Parameter description: Specifies whether to allow concurrent update.

Type: USERSET

Value range: Boolean

  • on indicates it is enabled.
  • off indicates it is disabled.

Default value: on

gtm_backup_barrier

Parameter description: Specifies whether to create a restoration point for the GTM starting point.

Type: SUSET

Value range: Boolean

  • on indicates that a restoration point will be created for the GTM starting point.
  • off indicates that a restoration point will not be created for the GTM starting point.

Default value: off

gtm_conn_check_interval

Parameter description: Sets the CN to check whether the connection between the local thread and the primary GTM is normal.

Parameter type: SIGHUP

Value range: an integer ranging from 0 to INT_MAX/1000. The unit is second.

Default value: 10s

transaction_deferrable

Parameter description: Specifies whether to delay the execution of a read-only serial transaction without incurring an execution failure. Assume this parameter is set to on. When the server detects that the tuples read by a read-only transaction are being modified by other transactions, it delays the execution of the read-only transaction until the other transactions finish modifying the tuples. Currently, this parameter is not used in GaussDB(DWS). Similar to this parameter, the default_transaction_deferrable parameter is used to specify whether to allow delayed execution of a transaction.

Type: USERSET

Value range: Boolean

  • on indicates that the execution of a read-only serial transaction can be delayed.
  • off indicates that the execution of a read-only serial transaction cannot be delayed.

Default value: off

enforce_two_phase_commit

Parameter description: This parameter is reserved for compatibility with earlier versions. This parameter is invalid in the current version.

enable_show_any_tuples

Parameter description: This parameter is available only in a read-only transaction and is used for analysis. When this parameter is set to on/true, all versions of tuples in the table are displayed.

Type: USERSET

Value range: Boolean

  • on/true indicates that all versions of tuples in the table are displayed.
  • off/false indicates that no versions of tuples in the table are displayed.

Default value: off

gtm_connect_retries

Parameter description: Specifies the number of GTM reconnection attempts.

Type: SIGHUP

Value range: an integer ranging from 1 to 2147483647.

Default value: 30

enable_redistribute

Parameter description: Specifies whether unmatched nodes are redistributed.

Type: SUSET

Value range: Boolean

  • on indicates that unmatched nodes are redistributed.
  • off indicates that unmatched nodes are not redistributed.

Default value: off