Persistent Store Format Changes

Version 3.7 UR1 of Message Queue introduced two changes to the persistent store format to improve performance. One change is to the file store, the other is to the JDBC store.

• Format of Transaction Data Persisted in File Store

  The format of transaction state information stored in the Message Queue file-based persistent store was changed to reduce disk I/O and to improve the performance of JMS transactions.

• Oracle JDBC Store

  In previous versions of Message Queue, the store schema for Oracle used the LONG RAW data type to store message data. In Oracle 8, Oracle introduced the BLOB data types and deprecated the LONG RAW type. Message Queue 3.7 UR1 switched to the BLOB data type to improve performance and supportability.

Because these changes impact store compatibility, the store version for both the file store and the JDBC store was changed from 350 to 370 in version 3.7 UR1 of Message Queue.

Version 4.0 of Message Queue introduced changes to the JDBC store for optimization and to support future enhancements. For this reason the JDBC store version was increased to 400. Note that in Version 4.0, the file-based persistent store version remains 370 because no changes were made to it.

Message Queue 4.0 supports automatic conversion of the persistent store to the newest versions of the file-based and JDBC persistent stores. The first time imqbrokerd starts, if the utility detects an older store it will migrate the store to the new format, leaving the old store behind.

• File-based store versions 200 and 350 will be migrated to the 370 version format.

• JDBC store versions 350 and 370 will be migrated to the 400 version format. (If you need to upgrade a 200 store, you will need to step through an intermediate 3.5 or 3. 6 release.)

If you should need to roll back this upgrade, you can uninstall Message Queue 4.0 and then reinstall the version you were previously running. Since the older copy of the store is left intact, the broker can run with the older copy of the store.