Administration Guide

Additional Space Requirements

Additional space is also required as follows:

• "Log File Space"
• "Temporary Work Space"

Log File Space

The amount of space (in bytes) required for log files can range from:

   ( logprimary * (logfilsiz + 2 ) * 4096 ) + 8192

to:

   ( (logprimary + logsecond) * (logfilsiz + 2 ) * 4096 ) + 8192

where:

• logprimary is the number of primary log files as defined in the database configuration file (see "Number of Primary Log Files (logprimary)")
• logsecond is the number of secondary log files as defined in the database configuration file (see "Number of Secondary Log Files (logsecond)")
• logfilsiz is the number of pages in each log file as defined in the database configuration file (see "Size of Log Files (logfilsiz)")
• 2 is the number of header pages required for each log file
• 4096 is the number of bytes in one page
• 8192 is the size (in bytes) of the log control file.

The upper limit of log space is dependent on the actual number of secondary log files that the database manager requires at run time. This upper limit may never be used or may only be used during occasional periods of high-volume activity.

Note:

If the database is enabled for roll-forward recovery, special log space requirements should be considered:

• With the logretain configuration parameter enabled, the log files will be archived in the log path directory. The on-line disk space will eventually fill up, unless you move the log files to a different location.
• With the userexit configuration parameter enabled, a user exit program moves the archived log files to a different location. Extra log space is still required to allow for:
  • On-line archived logs that are waiting to be moved by the user exit program
  • New log files being formatted for future use.

Temporary Work Space

Some SQL statements require temporary tables for processing (such as a work file for sorts that cannot be done in memory). These require disk space for storage during the time they are used. The amount required will be totally dependent on the queries and the size of tables returned, and therefore cannot be estimated.

You can use the database system monitor and query table space APIs to help you observe the amount of work space being used during the normal course of operations.

[ DB2 List of Books | Search the DB2 Books ]