Data Store Formats

Changes in the file formats for both file-based and JDBC-based persistent data stores were introduced in Message Queue 3.7, with further JDBC changes in version 4.0 and 4.1. As a result of these changes, the persistent data store version numbers have been updated to 370 for file-based data stores and 410 for JDBC-based stores. You can use the imqdbmgr query command to determine the version number of your existing data store.

On first startup, the Message Queue Broker utility (imqbrokerd) will check for the presence of an older persistent data store and automatically migrate it to the latest format:

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

• JDBC-based data store versions 350, 370, and 400 are migrated to the version 410 format. (If you need to upgrade a version 200 data store, you will need to step through an intermediate Message Queue 3.5 or 3.6 release.)

The upgrade leaves the older copy of the persistent data store intact, allowing you to roll back the upgrade if necessary. To do so, you can uninstall the current version of Message Queue and reinstall the earlier version you were previously running. The older version’s message brokers will locate and use the older copy of the data store.

Beginning in Message Queue 4.5, the imq.persist.file.newTxnLog property is true by default. This setting can generate an error when starting a broker that is using an older persistent data store. To resolve the error, set the property value to false and start the broker, thus migrating the data store to the latest format. Then, you can stop the broker, set the property value back to true, and start the broker without encountering an error.