Journal management concepts

This topic explains how journal management works, why to use it, and how it affects your system.

Journal management enables you to recover the changes to an object that have occurred since the object was last saved. You can also use journal management to provide an audit trail or to help replicate an object. You use a journal to define what objects you want to protect with journal management. The system keeps a record of changes you make to objects that are journaled and of other events that occur on the system.

This topic provides information about how journals work, information about journal entries, and how journals affect system performance.

• Benefits of journal management
  The primary benefit of journal management is that it enables you to recover the changes to an object that have occurred since the object was last saved. This ability is especially useful if you have an unscheduled outage such as a power failure.
• How journal management works
  Use journal management to create an object called a journal. Use a journal to define which objects you want to protect. You can have more than one journal on your system. A journal can define protection for more than one object.
• Journal entries
  When you use journal management, the system keeps a record of changes that you make to objects that are journaled and of other events that occur on the system. These records are called journal entries. You can use journal entries to help recover objects or analyze changes that were made to the objects.
• Journal management and system performance
  Journal management prevents transactions from being lost if your system ends abnormally or has to be recovered. To do this, journal management writes changes to journaled objects immediately to the journal receiver in auxiliary storage. This increases the disk activity on your system and can have a noticeable affect on system performance. Journaling also increases the overhead associated with opening objects and closing objects.
• Journal management with the save-while-active function
  Journaling can help you with recovery if you use the save-while-active function in your backup strategy. If you plan to save an application without ending it for checkpoint processing, consider journaling all of the objects associated with the application. After the save operation is complete, save all of the journal receivers for the objects you are saving.