[AlwaysOn] 創建SQL Server高可用性組T-SQL語法：AVAILABILITY_MODE參數

AVAILABILITY_MODE = { SYNCHRONOUS_COMMIT | ASYNCHRONOUS_COMMIT | CONFIGURATION_ONLY }

同步提交或異步提交指定在主副本可以提交給定主數據庫上的事務之前，主副本是否必須等待輔助副本確認將日志記錄硬化(寫入)到磁盤。SYNCHRONOUS_COMMIT or ASYNCHRONOUS_COMMIT specifies whether the primary replica has to wait for the secondary replica to acknowledge the hardening (writing) of the log records to disk before the primary replica can commit the transaction on a given primary database. 同一主副本上不同數據庫上的事務可以獨立提交。The transactions on different databases on the same primary replica can commit independently. SQL Server 2017 CU 1引入僅配置選項。SQL Server 2017 CU 1 introduces CONFIGURATION_ONLY.僅配置副本僅適用于群集類型為“外部”或“無”的可用性組。CONFIGURATION_ONLY replica only applies to availability groups with CLUSTER_TYPE = EXTERNAL or CLUSTER_TYPE = NONE.

同步提交 SYNCHRONOUS_COMMIT

指定主副本等待提交事務，直到在此次副本(同步提交模式)上對它們進行了固化。Specifies that the primary replica waits to commit transactions until they have been hardened on this secondary replica (synchronous-commit mode). 您可以為最多三個副本(包括主副本)指定同步提交。You can specify SYNCHRONOUS_COMMIT for up to three replicas, including the primary replica.

異步提交 ASYNCHRONOUS_COMMIT

指定主副本提交事務而不等待輔助副本固化日志(同步提交可用性模式)。Specifies that the primary replica commits transactions without waiting for this secondary replica to harden the log (synchronous-commit availability mode). 您可以為最多五個可用性副本(包括主副本)指定異步提交。You can specify ASYNCHRONOUS_COMMIT for up to five availability replicas, including the primary replica.

CONFIGURATION_ONLY

指定主副本將可用性組配置元數據同步提交到此副本上的主數據庫。Specifies that the primary replica synchronously commit availability group configuration metadata to the master database on this replica. 副本將不包含用戶數據。The replica will not contain user data. 此選項：This option:

l   可以托管在任何版本的SQL Server上，包括Express版本。Can be hosted on any edition of SQL Server, including Express Edition.

l   要求配置唯一副本的數據鏡像終結點為見證類型。Requires the data mirroring endpoint of the CONFIGURATION_ONLY replica to be type WITNESS.

l   不能更改。Can not be altered.

l   當集群類型為WSFC時無效。Is not valid when CLUSTER_TYPE = WSFC.

有關詳細信息，請參閱僅配置副本。For more information, see Configuration only replica.

AVAILABILITY_MODE 子句是必需的。The AVAILABILITY_MODE clause is required.有關詳細信息，請參閱可用性模式(始終在可用性組上)。For more information, see Availability Modes (Always On Availability Groups).