ORACLE FAILOVER_MODE Parameters

Oracle rac tnsnames.ora配置中经常会用到 FAILOVER_MODE参数，这里摘录一下，仅供参考

引用

The FAILOVER_MODE parameter must be included in the CONNECT_DATA section of a connect descriptor. FAILOVER_MODE can contain the subparameters described in Table

BACKUP


Specify a different net service name for backup connections. A backup should be specified when using preconnect to pre-establish connections.

TYPE


Specify the type of failover. Three types of Oracle Net failover functionality are available by default to Oracle Call Interface (OCI) applications:

    *

      session: Set to failover the session. If a user's connection is lost, a new session is automatically created for the user on the backup. This type of failover does not attempt to recover selects.
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      select: Set to enable users with open cursors to continue fetching on them after failure. However, this mode involves overhead on the client side in normal select operations.
    *

      none: This is the default. No failover functionality is used. This can also be explicitly specified to prevent failover from happening.

METHOD


Determines how fast failover occurs from the primary node to the backup node:

    *

      basic: Set to establish connections at failover time. This option requires almost no work on the backup server until failover time.
    *

      preconnect: Set to pre-established connections. This provides faster failover but requires that the backup instance be able to support all connections from every supported instance.

RETRIES


Specify the number of times to attempt to connect after a failover. If DELAY is specified, RETRIES defaults to five retry attempts.

Note: If a callback function is registered, then this subparameter is ignored.

DELAY


Specify the amount of time in seconds to wait between connect attempts. If RETRIES is specified, DELAY defaults to one second.

Note: If a callback function is registered, then this subparameter is ignored.