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• The amount of time to cover with all logs (Time 1 up to Current Time)
• The amount of time to cover with active logs (Time 2 up to Current Time)
Figure 5. DB2 Log and Its Data Sets
3.6.3 Archive Logs
Archive log data sets are DB2 managed backups of the active log data sets.
Archive log data sets are created automatically by DB2 whenever an active log is
filled. They may also be created with the -ARCHIVE command for operational
requirements. Additional circumstances may trigger the archiving process. The
DB2 for OS/390 Administration Guide, SC26-8957, describes these in detail.
DB2 supports dual archive logs and it is recommended to use dual archive log
data sets for all production environments. When dual archive log is specified,
during the archiving, the primary active log is read and two archive log data sets
are written in parallel. For better archive log availability, customers should define
both copies on different devices (or SMS classes) to physically separate the dual
data sets.
Archive log data sets are required for any recovery that spans a period of time in
excess of the time covered by the active logs. Archive log data sets are
sequential data sets that can be:
• Defined on disk or on tape
•Migrated
• Deleted with standard procedures
Archive log data sets are required for data integrity. Procedures are required to
ensure that archive log data sets are only deleted when they are not going to be
required anymore.
This book contains references related to archive log deletes, in the following
sections:
• “Deleting Image Copies and Archive Logs” on page 21.
• “Impact of Log Size on Backup and Recovery Strategy” on page 18.
DB2 LOG
ACTIVE LOG
ARCHIVE + ACTIVE LOG
Start
Time
Time
1
Time
2
Current
Time