Performance Tuning for Content Manager

Chapter 8. Tuning DB2 for Content Manager 245

Our recommendation

The Content Manager installation program changes this value to 30.

Initially, use this value. In our test, we did not run into any lock timeout issues and

thus did not need to change this value.

You can use the database system monitor to help you track the number of times

an application (connection) experienced a lock timeout, or that a database

detected a timeout situation for all applications that were connected.

High values of the lock_timeout (number of lock time-outs) monitor element can

be caused by:

 Too low a value for this configuration parameter.

 An application (transaction) that holds locks for an extended period. You can

use the database system monitor to further investigate these applications.

 A concurrency problem, which could be caused by lock escalations (from

row-level to a table-level lock).

8.6.35 Size of the log files (LOGFILSIZ)

Impact

DB - Medium

Description

This parameter defines the size of primary and secondary log files. The primary

log file is preallocated at this specified value. The size of these log files limits the

number of log entries that can be written to them before they become full and

new log files are required.

The use of primary and secondary log files, as well as the action taken when a log

file becomes full, are dependent on the type of logging that is being performed:

 Circular logging

A primary log file can be reused when the changes recorded in it have been

committed. If the log file size is small and applications have processed a large

number of changes to the database without committing the changes, a primary

log file can quickly become full. If all primary log files become full, the

database manager will allocate secondary log files to hold the new log records.

 Log retention logging

When a primary log file is full, it is archived and a new primary log file is

allocated.

246 Performance Tuning for Content Manager

Default values (range)

1,000 (4 - 262,144) 4-KB pages for UNIX platforms

250 (4 - 262,144) 4-KB pages for Windows platforms

To update

Run the following command:

db2 update db cfg for <database name> using LOGFILSIZ <parameter value>

Our recommendation

The Content Manager installation program changes this value to 1,000 for

Library Server database in both Windows and AIX platforms.

You must balance the size of the log files with the number of primary log files.

Larger log files provide better performance but potentially increase the degree of

lost transactions in case of system crash or a lost log file.

If your system has a large number of write activities such as update, insert, and

delete transactions, you might increase this parameter value because the log

files can become full too quickly in this environment.

If the log file size is set too small, it could create too much overhead for the

system to constantly archive old log files and create new ones.

If the size is set too large, it could take a long time for the system to create new

log files. Working with large log files can also be inconvenient because some text

editors might not be able to display files that exceed certain size limits. Large log

files also take up a lot of disk space. You might need to reduce the parameter

value if disk space is scarce, because primary logs are preallocated at this size.

Note: The upper limit of log file size, combined with the upper limit of the

number of log files (LOGPRIMARY + LOGSECOND), gives an upper limit of

256 GB of active log space.

Note: If you are using log retention, the current active log file is closed and

truncated when the last application disconnects from a database. Try to use a

log file size, which will not allocate excessive amounts of wasted space.