Disabling Fast-Start Failover

Nel documento Oracle® Data Guard Broker 10g (pagine 97-100)

Switchover and Failover Operations

Step 5 Reinstate the former primary database as a new standby database

5.5.4 Disabling Fast-Start Failover

Disabling fast-start failover prevents the observer from initiating a failover to the target standby database. In this case, manual failover may still be possible. See Section 5.4 for information about manual failover.

To disable fast-start failover, use the Fast-Start Failover wizard in Enterprise Manager or the DGMGRL DISABLE FAST_START FAILOVER [FORCE] command. The FORCE option disables fast-start failover on the database to which you are connected even when errors occur. Whether or not you use the FORCE option depends on if the primary and target standby database have network connectivity:

STALLED Displays on the primary database after loss of connectivity to the target standby database and the change to the UNSYNCHRONIZED state cannot be confirmed by either the target standby database or the observer.

It stalls because it is likely a failover has occurred. Note: this state also occurs during startup when fast-start failover is synchronized and neither the target standby database nor the observer are present to confirm it is okay to continue opening the database.

The primary database will not stall upon loss of connectivity to the target standby database if both the primary and standby databases lost connectivity to the observer more than a minute in the past. Fast-start failover is not possible in this case to allow the primary database to continue committing redo even though neither the target standby database nor the observer are present.

Is possible

PRIMARY UNOBSERVED

Displays only on the target standby database when it is SYNCHRONIZED with the primary database, has connectivity to the observer, but the primary database does not have a

connection to the observer. This is a rare state.

Is not possible

REINSTATE REQUIRED

The failed primary database requires

reinstatement as a new standby database to the new primary. The observer automatically starts the reinstatement process. REINSTATE REQUIRED is present only after fast-start failover has occurred and shows only on the new primary database.

Has completed

REINSTATE IN PROGRESS

Reinstatement of the failed primary database as a new standby database is in progress.

Has completed

REINSTATE FAILED

Reinstatement of the failed primary database as a new standby database failed. See Section 10.1 for details about the broker's drc* log files.

Has completed

Note: Disabling fast-start failover does not stop the observer. To stop the observer, see Section 5.5.6.4, "Stopping the Observer".

Table 5–2 (Cont.) FS_FAILOVER_STATUS Column of the V$DATABASE View

Column Value Description Fast-Start Failover ...

Fast-Start Failover

If the primary and target standby database have network connectivity, Oracle recommends that you use DISABLE FAST_START FAILOVER without the FORCE option. This method will disable fast-start failover on all databases in the broker configuration.

If errors occur during the disable operation, the broker returns an error message and stops the disable operation.

If the primary and target standby databases do not have network connectivity or if the database to which you are connected does not have network connectivity with the primary database, consider using DISABLE FAST_START FAILOVER with the FORCE option.

The broker may not be able to disable fast-start failover on all databases in the broker configuration when you issue the DISABLE FAST_START FAILOVER FORCE command. As a result, there is no guarantee that the observer will not perform a fast-start failover to the target standby database if the observer determines that conditions warrant a failover. The following list indicates the extent to which fast-start failover is disabled in the broker configuration when the DISABLE FAST_START FAILOVER FORCE command is issued on the primary database, target standby database, and a standby database that is not the fast-start failover target.

If you issue this command on:

The primary database, the primary database attempts to disable fast-start failover on as many databases in the configuration with which it has a network connection. If the primary database does not have connectivity with the target standby database, fast-start failover remains enabled on the target standby database and the observer may still attempt a fast-start failover if conditions warrant a failover.

The target standby database when it does not have connectivity with the primary database, fast-start failover is disabled only on the target standby database. In this case, the observer cannot perform a fast-start failover even if conditions warrant a failover. Disabling fast-start failover with the FORCE option when connected to the target standby database is the only method that guarantees fast-start failover will not occur.

If the primary database and the target standby database regain network connectivity, the broker will disable fast-start failover for the entire broker configuration.

Another standby database that does not have connectivity with the primary database, fast-start failover is disabled for this database. Because fast-start failover was not disabled on the target standby database, the observer may still attempt a fast-start failover to the target standby database should conditions warrant a failover.

Caution: This action may result in two databases in the

configuration simultaneously assuming the primary database role should fast-start failover occur.

Fast-Start Failover

Conditions Requiring the FORCE Option

Disabling fast-start failover without the FORCE option can succeed only if the database on which the command is issued has a network connection with the primary database and if the primary database and target standby database have a network connection.

This is the recommended method for disabling fast-start failover.

However, there may be situations in which you must disable fast-start failover when the primary database and the target standby database do not have a network connection, or the database on which you issued the disable fast-start failover

command does not have a network connection to the primary database. In cases where there is a lost network connection, be aware that the observer may attempt a fast-start failover to the target standby database if conditions warrant a failover.

The FORCE option may be the preferred method for disabling fast-start failover when:

A network outage isolates the primary database from the observer and the target standby database, while the databases are synchronized.

In this case, the primary database stalls and prevents any further transactions from committing because a fast-start failover may have occurred while it was isolated. If you expect the network to be disconnected for a long time, disable fast-start failover with the FORCE option on the primary database to allow processing to continue (without waiting for the connection to the target standby database or the observer computer to be restored).

If possible, confirm that fast-start failover has not occurred to the target standby database prior to disabling fast-start failover with the FORCE option on the primary database.

You want to conduct a manual failover to any standby database in the

configuration (for example, because a failure occurred on the primary database at a time when the primary and target standby database were not synchronized).

In this case fast-start failover cannot occur because the databases are not synchronized. You cannot perform a manual failover to the target standby database for the same reason. To proceed, you must first disable fast-start failover using the FORCE option, and then perform a manual failover.

Caution: When you are experiencing network disconnections and you issue the DISABLE FAST_START FAILOVER FORCE command on the primary database or a standby database that does not have connectivity with the primary database, fast-start failover may not be disabled for all databases in the broker configuration. As a result the observer may still initiate fast-start failover to the target standby database, if conditions warrant a failover. This may result in two databases in the configuration simultaneously assuming the primary database role.

Caution: This action may result in two databases in the

configuration simultaneously assuming the primary database role.

Caution: This action will result in loss of data and the possibility of two databases in the configuration simultaneously assuming the primary database role.

Fast-Start Failover

A fast-start failover to the target standby database fails.

If the failover fails for any reason, it could leave the target standby database inoperable, regardless of whether the target standby database is synchronized. If there is another standby database that is available for failover, you can perform a manual failover to that standby database after you first disable fast-start failover using the FORCE option on that standby database.

You want to prevent fast-start failover from occurring because the primary database will resume service soon.

In this case, disable fast-start failover using the FORCE option on the target standby database. Once the primary database regains connectivity with the target standby database, fast-start failover will be disabled for all the databases in the configuration.

Disabling Fast-Start Failover Using Enterprise Manager

Click Disable in the Fast-Start Failover wizard. Then, click Continue to proceed to the next page. See the Enterprise Manager online Help system for more information.

Disabling Fast-Start Failover Using DGMGRL

Issue the DISABLE FAST_START FAILOVER command or the DISABLE FAST_

START FAILOVER FORCE command. See the "DISABLE FAST_START FAILOVER"

command in Chapter 8 for more information.

Nel documento Oracle® Data Guard Broker 10g (pagine 97-100)