Journaling Catalogs

Journaling Cumulus catalogs improves data security. A journaling catalog logs changes to a journal (special circular log files) before actually writing them to the catalog. Such a journal is used to repair any inconsistencies that occur as a result of an improper shutdown of the Cumulus Server or the computer running the Cumulus Server. In the event of an improper shutdown, a given set of changes may have either been fully committed to the catalog (i.e., written to the hard disk), in which case there is no problem, or the changes will have been marked as not yet fully committed, in which case the system will read the journal, which can be rolled up to the most recent point of data consistency. Every time a Cumulus Server opens a catalog the journals will be read and executed.

A Cumulus catalog journal consists of circular log files named as the catalog file with the extension .redo. These files are saved along with the catalog file in the same folder and can become quite large. Therefore, you must make sure that there is enough free disk space available. As rule of thumb: twice the size of the catalog file, or at least 5 GB is recommended.

IMPORTANT! Copying or Moving Journaling Catalogs
When copying, moving or backing up a catalog externally, the journal of the catalog (all 5 *.redo log files) must be included, e.g. copied or moved along with the catalog file.

IMPORTANT! Using Backup Files Created by Cumulus
If you want to replace a damaged catalog file of a journaling catalog with a backup file created by Cumulus, you must delete the journal of the catalog (all 5 *.redo log files) before you copy and/or rename the backup file.