The Tivoli® Storage Manager server deletes unnecessary files from the archive log only when a full database backup occurs. Consequently, when you estimate the space that is required for the archive log, you must also consider the frequency of full database backups.
For example, if a full database backup occurs once a week, the archive log space must be able to contain the information in the archive log for a full week.
The difference in archive log size for daily and full database backups is shown in the example in the following table.
| Item | Example values | Description |
|---|---|---|
| Maximum number of client nodes that back up, archive, or migrate files concurrently at any time | 300 | The number of client nodes that back up, archive, or migrate files every night. |
| Files stored during each transaction | 4096 | The default value of the server option TXNGROUPMAX is 4096. |
| Log space that is required for each file | 3453 bytes | 3053 bytes for each file plus 200 bytes for
each copy storage pool. The value of 3053 bytes for each file in a transaction represents the log bytes needed when backing up files from a Windows client where the file names are 12 - 120 bytes. This value is based on the results of tests performed under laboratory conditions. Tests consisted of clients performing backup operations to a random-access disk (DISK) storage pool. DISK pools result in more log use than sequential-access storage pools. Consider a value larger than 3053 bytes if the data being stored has file names that are longer than 12 - 120 bytes. |
| Active log: Suggested size | 20 GB 1 | Use the following calculation to determine the size of the active log. One GB equals 1,073,741,824 bytes. (300 clients x 4096 files per transaction x 3453 bytes per file) ÷ 1,073,741,824 bytes = 4.0 GB Increase that amount by the suggested starting size of 16 GB: 4 + 16 = 20 GB |
| Archive log: Suggested size with a full database backup every day | 60 GB 1 | Because of the requirement to be able to store
archive logs across three backup cycles, multiply the estimate for
the active log by 3 to estimate the total archive log requirement: 4 GB x 3 = 12 GB Increase that amount by the suggested starting size of 48 GB: 12 + 48 = 60 GB |
| Archive log: Suggested size with a full database every week | 132 GB 1 | Because of the requirement to be able to store
archive logs across three server database-backup cycles, multiply
the estimate for the active log by 3 to estimate the total archive
log requirement. Multiply the result by the number of days between
full database backups: (4 GB x 3 ) x 7 = 84 GB Increase that amount by the suggested starting size of 48 GB: 84 + 48 = 132 GB |
| 1 The example values
in this table are used only to illustrate how the sizes for active
logs and archive logs are calculated. In a production environment
that does not use deduplication, 16 GB is the suggested minimum size
for an active log. The suggested starting size for an archive log
in a production environment that does not use deduplication is 48
GB. If you substitute values from your environment and the results
are larger than 16 GB and 48 GB, use your results to size the active
log and archive log. Monitor your logs and adjust their size if necessary. |
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