Oracle Distributed Systems

DBMS_SNAPSHOT: Managing Snapshots

The DBMS_SNAPSHOT package contains programs that allow you to maintain snapshots and snapshot logs and to set and query package state variables associated with the advanced replication facilities.

How the Package Is Used

The procedures I_AM_A_REFRESH and SET_I_AM_A_REFRESH are used to check and set the package variable REP$WHAT_AM_I.I_AM_A_SNAPSHOT, which numerous replication triggers and procedures reference. The procedures PURGE_LOG and REFRESH are typically run by the DBA and/or scheduled in the job queue.

Installation and Access

The DBMS_SNAPSHOT package is created when the Oracle database is installed. The dbmssnap.sqlscript (found in the built-in packages source directory) contains the source code for this package’s specification. This script is called by catproc.sql, which is normally run immediately after database creation. The script creates the public synonym DBMS_SNAPSHOT for the package and grants the EXECUTE privilege on the package to public. All Oracle users can reference and make use of this package.

DBMS_SNAPSHOT Procedures

Name	Description
BEGIN_TABLE_REORGANIZATION (Oracle8 only)	Called prior to reorganizing a master table (e.g., through export/import); saves data required to refresh snapshots
END_TABLE_REORGANIZATION (Oracle8 only)	Called after reorganizing a master table (e.g., through export/import); validates data required to refresh snapshots
I_AM_A_REFRESH	Returns value of REP$WHAT_AM_I.I_AM_A_SNAPSHOT
PURGE_LOG	Purges snapshot ...