Active and archive logs

Db2 records all data changes and other significant events in a log.

If you keep these logs, Db2 can re-create those changes for you in the event of a failure or roll the changes back to a previous point in time.

Db2 writes each log record to a disk data set called the active log. When the active log is full, Db2 copies the contents of the active log to a disk or magnetic tape data set called the archive log.

You can choose either single logging or dual logging.

• A single active log contains up to 93 active log data sets.
• With dual logging, the active log has twice the capacity for active log data sets, because two identical copies of the log records are kept.

Each Db2 subsystem manages multiple active logs and archive logs. The following facts are true about each Db2 active log:

• Each log can be duplexed to ensure high availability.
• Each active log data set is a VSAM linear data set (LDS).
• Db2 supports striped active log data sets, however striping is generally unnecessary with the latest devices, and is not recommended in most cases.
  Important: Do not use striped active logs for disaster recovery.