Number of Primary Log Files (logprimary)

Configuration Type

Database

Parameter Type

Configurable

Default [Range]

3 [ 2 - 128 ]

Unit of Measure

Counter

When Allocated

• The database is created

• A log is moved to a different location (which occurs when the logpath parameter is updated)

• Following a increase in the value of this parameter (logprimary), during the next database connection after all users have disconnected

• A log file has been archived and a new log file is allocated (the logretain or userexit parameter must be enabled)

• If the logfilsiz parameter has been changed, the active log files are re-sized during the next database connection after all users have disconnected.

When Freed

Not freed unless this parameter decreases. If decreased, unneeded log files are deleted during the next connection to the database.

Related Parameters

• Size of Log Files (logfilsiz)
• Number of Secondary Log Files (logsecond)
• Log Retain Enable (logretain)
• User Exit Enable (userexit)

The primary log files establish a fixed amount of storage allocated to the recovery log files. This parameter allows you to specify the number of primary log files to be preallocated.

Under circular logging, the primary logs are used repeatedly in sequence. That is, when a log is full, the next primary log in the sequence is used if it is available. A log is considered available if all units of work with log records in it have been committed or rolled-back. If the next primary log in sequence is not available, then a secondary log is allocated and used. Additional secondary logs are allocated and used until the next primary log in the sequence becomes available or the limit imposed by the logsecond parameter is reached. These secondary log files are dynamically deallocated as they are no longer needed by the database manager.

The number of primary and secondary log files must comply with the following equation:

• (logprimary + logsecond) <= 128

Recommendation: The value chosen for this parameter depends on a number of factors, including the type of logging being used, the size of the log files, and the type of processing environment (for example, length of transactions and frequency of commits).

Increasing this value will increase the disk requirements for the logs because the primary log files are preallocated during the very first connection to the database.

If you find that secondary log files are frequently being allocated, you may be able to improve system performance by increasing the log file size (logfilsiz) or by increasing the number of primary log files.

For databases that are not frequently accessed, in order to save disk storage, set the parameter to 2. For databases enabled for roll-forward recovery, set the parameter larger to avoid the overhead of allocating new logs almost immediately.

You may use the database system monitor to help you size the primary log files.

For more information see

• Maximum Secondary Log Space Used
• Maximum Total Log Space Used
• Secondary Logs Allocated Currently.

Observation of these monitor values over a period of time will aid in better tuning decisions, as average values may be more representative of your ongoing requirements.