The size of the transaction log must be checked regularly to work out how much free space is available on the log disk. There should always be enough free space to allow the next file extension. When the SAP system has been installed the autogrow increment is set. At least the size of this increment should be available on the log disk to permit the next file extension. If less space is available and the transaction log file fills up, the SAP system will come to a standstill.
Ideally, the transaction log should never be filled to more than 60-70%. If the transaction log regularly exceeds this level between 2 transaction log backups, the transaction log must be saved at more frequent time intervals.
The size of the log can be assessed on the basis of information given for completed backups in the SAP transaction for Backup and Restore Information.
1. To access the transaction for Backup Restore Information choose CCMS ® DB Administration ® Backup logs.
Alternatively, enter the transaction code DB12.
The initial screen of the monitor CCMS Monitoring Tool – DB12 (Backup Restore Information) appears.
2. Choose Backup history and then Logs Backup.
3. A result list appears. Find the largest transaction log backup of the past week. Select a row and then History info to find out the number of pages that were processed during the backup. To work out the amount of space used in the transaction log, multiply the number of dumped pages by 8 KB. You can then work out how much free space is left on the transaction log disk.
If you use a RAID1 disk system exclusively for the SAP transaction log and create hourly log backups, you will rarely encounter space problems. The SAP log file is initially created with a size of 1 GB. The smallest disk normally has 9 GB space and the log file can therefore grow to 9 GB.