For a given level of system activity, the less logical-log disk space that you allocate, the sooner that logical-log space fills up, and the greater the likelihood that user activity is blocked due to logical-log backups and checkpoints, as follows:
When the logical-log files that make up the logical log fill, you have to back them up. The backup process can hinder transaction processing that involves data located on the same disk as the logical-log files. If enough logical-log disk space is available, however, you can wait for periods of low user activity before you back up the logical-log files. (See Backup of Logical-Log Files.)
At least one checkpoint record must always be written to the logical log. If you need to free the logical-log file that contains the last checkpoint, the database server must write a new checkpoint record to the current logical-log file. If the frequency with which logical-log files are backed up and freed increases, the frequency at which checkpoints occur increases. Although checkpoints block user processing, they no longer last as long. Because other factors (such as the physical-log size) also determine the checkpoint frequency, this effect might not be significant. (See Freeing of Logical-Log Files.)
Whether tables use logging also affects the rate at which the logical log fills.
These performance considerations are related to how fast the logical log fills. The rate at which the logical log fills, in turn, depends on other factors such as the level of user activity on your system. You need to tune the logical-log size, therefore, to find the optimum value for your system.
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