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Oracle® In-Memory Database Cache User's Guide
Release 11.2.1

Part Number E13073-08
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8 Cleaning up the Caching Environment

This chapter describes the various tasks that need to be performed in the TimesTen and Oracle databases to destroy a cache grid and drop cache groups. It includes the following topics:

Detaching a TimesTen database from a cache grid

Call the ttGridDetach built-in procedure to detach a grid member from the cache grid that it is attached to. If the grid member is an active standby pair, both the active master and standby master databases must be detached separately. When a grid member has been detached, you can no longer perform operations on its global cache groups or on their cache tables. The grid member also relinquishes ownership of all cache instances that it had owned. The cache agent and replication agent processes cannot be stopped until the database detaches from its cache grid.

From the cachealone1, cachealone2, cacheactive and cachestandby databases, call the ttGridDetach built-in procedure as the cache manager user to detach the member from the ttGrid cache grid. The following example shows the built-in procedure call from the cachealone1 database:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttGridDetach;

Use the ttRepSubscriberWait built-in procedure to make sure that all committed updates on cache tables in its global cache groups have been propagated to the cached Oracle tables before the TimesTen database is detached from its cache grid.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttRepSubscriberWait('_AWTREPSCHEME','TTREP','_ORACLE','sys1',-1);

Then after the database has been detached from its grid, the replication agent running on the database can be stopped.

You can force detach a grid member that becomes unavailable but is still attached to the grid. A grid member's underlying TimesTen database is unavailable, for example, when the TimesTen system is taken offline or the database has been destroyed. Call the ttGridDetach built-in procedure as the cache manager user passing the value 1 to the force parameter from any one of the TimesTen databases that are available except from the read-only subscriber databases.

Command> call ttGridDetach('TTGRID_alone2_2',1);

To determine the names of all attached grid members, call the ttGridNodeStatus built-in procedure.

You can force detach a set of grid members that become unavailable but are still attached to the grid by calling the ttGridDetachList built-in procedure as the cache manager user from any one of the TimesTen databases that are available except from the read-only subscriber databases. Pass the value 1 to the force parameter.

Command> call ttGridDetachList('TTGRID_cacheact_3A TTGRID_cachestand_3B',1);

You can detach all of the grid members by calling the ttGridDetachAll built-in procedure:

Command> call ttGridDetachAll();

Stopping the replication agent

Call the ttRepStop built-in procedure to stop the replication agent. This must be done on each TimesTen database of the active standby pair including any read-only subscriber databases, and any standalone TimesTen databases that contain AWT cache groups.

From the cachealone1, cachealone2, cacheactive, cachestandby and rosubscriber databases, call the ttRepStop built-in procedure as the cache manager user to stop the replication agent on the database:

Command> call ttRepStop;

Dropping a cache group

Use the DROP CACHE GROUP statement to drop a cache group and its cache tables. Oracle objects used to manage the caching of Oracle data are automatically dropped when you use the DROP CACHE GROUP statement to drop a cache group, or an ALTER CACHE GROUP statement to set the automatic refresh state to OFF for automatic refresh cache groups.

If you issue a DROP CACHE GROUP statement on a cache group that has an automatic refresh operation in progress:

If cache tables are being replicated in an active standby pair and the cache tables are the only elements that are being replicated, the active standby pair must be dropped using a DROP ACTIVE STANDBY PAIR statement before dropping the cache groups.

An active standby pair replication scheme cannot be dropped from a TimesTen database if that database is still attached to a cache grid.

Execute the following statement as the cache manager user on the cacheactive, cachestandby and rosubscriber databases to drop the active standby pair replication scheme:

Command> DROP ACTIVE STANDBY PAIR;
Command> exit

Before you can drop a cache group, you must grant the DROP ANY TABLE privilege to the cache manager user.

Execute the following statement as the instance administrator on the cachealone1, cachealone2, cacheactive and cachestandby databases to grant the DROP ANY TABLE privilege to the cache manager user. The following example shows the SQL statement issued from the cachealone1 database:

% ttIsql cachealone1
Command> GRANT DROP ANY TABLE TO cacheuser;
Command> exit

Use a DROP CACHE GROUP statement to drop the cache groups from the standalone TimesTen databases, and the active master and standby master databases.

Execute the following statement as the cache manager user on the cachealone1, cachealone2, cacheactive and cachestandby databases to drop the subscriber_accounts global cache group. The following example shows the SQL statement issued from the cachealone1 database:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> DROP CACHE GROUP subscriber_accounts;

If you are dropping an AWT cache group, use the ttRepSubscriberWait built-in procedure to make sure that all committed updates on its cache tables have been propagated to the cached Oracle tables before dropping the cache group.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttRepSubscriberWait('_AWTREPSCHEME','TTREP','_ORACLE','sys1',-1);

The replication scheme that was created for the AWT cache group to enable committed updates on its cache tables to be asynchronously propagated to the cached Oracle tables is automatically dropped when you drop the cache group.

If a grid member has a global cache group that contains cache instances, the cache group cannot be dropped until all of its cache tables are empty or the member has detached from its cache grid.

Note:

If the cache agent is stopped immediately after dropping a cache group, or altering the cache group's automatic refresh state to OFF, the Oracle objects used to manage the caching of Oracle data may not have been dropped. When the cache agent is restarted, it drops the Oracle objects that were created for the dropped or altered cache group.

Destroying a cache grid

Call the ttGridDestroy built-in procedure to destroy a cache grid. By default, a cache grid cannot be destroyed if there are existing global cache groups or attached grid members.

From any one of the TimesTen databases, except from the read-only subscriber databases, call the ttGridDestroy built-in procedure as the cache manager user to destroy the ttGrid cache grid:

Command> call ttGridDestroy('ttGrid');

You can force destroy a cache grid even if a grid member whose TimesTen database becomes unavailable while it contains global cache groups or is attached to the grid. A TimesTen database is unavailable, for example, when the TimesTen system is taken offline or the database has been destroyed. Call the ttGridDestroy built-in procedure as the cache manager user passing the value 1 to the force parameter from any one of the TimesTen databases except from the read-only subscriber databases.

Command> call ttGridDestroy('ttGrid',1);

A cache grid should be destroyed only if it is no longer needed and there is no intent to attach to it again.

Stopping the cache agent

Call the ttCacheStop built-in procedure to stop the cache agent. This must be done on the active master and standby master databases of the active standby pair, and all standalone TimesTen databases.

From the cachealone1, cachealone2, cacheactive and cachestandby databases, issue the following built-in procedure call to stop the cache agent on the database:

Command> call ttCacheStop;
Command> exit

The cache agent cannot be stopped if the TimesTen database is still attached to a cache grid.

Destroying the TimesTen databases

If the TimesTen databases are no longer needed, you can use the ttDestroy utility to destroy the databases.

The following example shows the ttDestroy utility connecting to and then destroying the cachealone1 database:

% ttDestroy cachealone1

Dropping the Oracle users and objects

Use SQL*Plus as the sys user to drop the timesten user, the schema user oratt, and the cache administration user cacheuser, and all objects such as tables and triggers owned by these users. Then drop the TT_CACHE_ADMIN_ROLE role, and the default tablespace cachetblsp used by the timesten user and the cache administration user including the contents of the tablespace and its data file.

% sqlplus sys as sysdba
Enter password: password
SQL> DROP USER timesten CASCADE;
SQL> DROP USER oratt CASCADE;
SQL> DROP USER cacheuser CASCADE;
SQL> DROP ROLE tt_cache_admin_role;
SQL> DROP TABLESPACE cachetblsp INCLUDING CONTENTS AND DATAFILES;
SQL> exit