ALTER CACHE GROUP

The ALTER CACHE GROUP statement allows changes to the state, interval and mode of AUTOREFRESH.

Updates on Oracle tables can be propagated back to the TimesTen cache group with the use of AUTOREFRESH. AUTOREFRESH can be enabled when the cache group is a user managed cache group or is defined as READONLY with an AUTOREFRESH clause.

Any values or states set by ALTER CACHE GROUP are persistent. They are stored in the data store and survive daemon and cache agent restarts.

For a description of cache group types, see "User managed and system managed cache groups".

Required privilege

No privilege is required for the cache group owner.

ALTER ANY CACHE GROUP for another user's cache group.

SQL syntax

This statement changes the AUTOREFRESH mode of the cache group, which determines which rows are updated during an autorefresh operation:

ALTER CACHE GROUP [Owner.]GroupName
        SET AUTOREFRESH MODE
        {INCREMENTAL | FULL}

This statement changes the AUTOREFRESH interval on the cache group:

ALTER CACHE GROUP [Owner.]GroupName 
        SET AUTOREFRESH INTERVAL IntervalValue 
        {MINUTE[S] | SECOND[S] | MILLISECOND[S] }

This statement alters the AUTOREFRESH state:

ALTER CACHE GROUP [Owner.]GroupName 
        SET AUTOREFRESH STATE
        {ON | OFF | PAUSED}

Parameters

ALTER CACHE GROUP has the parameters:

Parameter	Description
[`Owner.]GroupName`	Name assigned to the new cache group.
`AUTOREFRESH`	Indicates that changes to Oracle tables should be automatically propagated to TimesTen. For details, see "AUTOREFRESH in cache groups".
`MODE`	Determines which rows in the cache are updated during an autorefresh. If the INCREMENTAL clause is specified, TimesTen refreshes only rows that have been changed on Oracle since the last propagation. If the FULL clause is specified or if there is neither FULL nor INCREMENTAL clause specified, TimesTen updates all rows in the cache with each autorefresh. The default mode is INCREMENTAL.
`INTERVAL` `IntervalValue`	Indicates the interval at which autorefresh should occur in units of minutes, seconds or milliseconds. An integer value that specifies how often AUTOREFRESH should be scheduled, in minutes, seconds or milliseconds. The default value is 10 minutes. If the specified interval is not long enough for an AUTOREFRESH to complete, a runtime warning is generated and the next AUTOREFRESH waits until the current one finishes. An informational message is generated in the support log if the wait queue reaches 10.
`STATE`	Specifies whether AUTOREFRESH should be changed to on, off or paused. By default, the AUTOREFRESH STATE is on.
`ON`	AUTOREFRESH is scheduled to occur at the specified -interval.
`OFF`	A scheduled AUTOREFRESH is cancelled, and TimesTen does not try to maintain the information necessary for an INCREMENTAL refresh. Therefore if AUTOREFRESH is turned on again at a later time, the first refresh is FULL.
`PAUSED`	A scheduled AUTOREFRESH is cancelled, but TimesTen tries to maintain the information necessary for an INCREMENTAL refresh. Therefore if AUTOREFRESH is turned on again at a later time, a full refresh may not be necessary.

Description

A refresh does not occur immediately after issuing ALTER CACHE GROUP...SET AUTOREFRESH STATE. This statement only changes the state of AUTOREFRESH. When the transaction that contains the ALTER CACHE GROUP statement is committed, the cache agent is notified to schedule an AUTOREFRESH immediately, but the commit goes through without waiting for the completion of the refresh. The scheduling of the autorefresh operation is part of the transaction, but the refresh itself is not.
If you issue an ALTER CACHE GROUP... SET AUTOREFRESH STATE OFF statement and there is an autorefresh operation currently running, then:
- If LockWait interval is 0, the ALTER statement fails with a lock timeout error.
- If LockWait interval is non-zero, then the current autorefresh transaction is rolled back, and the ALTER statement continues. This affects all cache groups with the same autorefresh interval.
Replication cannot occur between cache groups with AUTOREFRESH and cache groups without AUTOREFRESH.
If the ALTER CACHE GROUP statement is part of a transaction that is being replicated, and if the replication scheme has the RETURN TWOSAFE attribute, the transaction may fail.