Why DB2 did not reuse/rename the transaction logs even after they have been successfully archived?

Technote (FAQ)


Question

Why DB2 did not reuse/rename the (full size) transaction logs even after they have been successfully archived?

Cause

If a log file is archived and contains no open transactions, the DB2 database manager does not delete the file but renames it as the next log file when such a file is needed. This process improves performance because creating a new log file instead of renaming the file would require all pages to be written out to guarantee that the necessary disk space or other storage space is available.

The database manager retains up to 8 extra log files in the active log path for renaming purposes.

Aim is that there is existing log file can be used to rename when high workload comes:
(1) at that point the log consumption will become very quickly.
(2) creating new log file is a high cost operation since DB2 need to write to log file in advance, otherwise, the disk space may not be actually allocated to DB2.

Answer

You can collect "db2pd -db <database> -dpsdbcb" data.

Please provide the output file of db2pd command to IBM DB2 Service to check rename array for confirmation.


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Document information


More support for:

DB2 for Linux, UNIX and Windows

Software version:

8.2, 9.1, 9.5, 9.7, 9.8, 10.1, 10.5

Operating system(s):

AIX, HP-UX, Linux, Solaris, Windows

Reference #:

1644647

Modified date:

2013-07-23

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