Adaptive Server version 11.9 and later include rollback records in the transaction logs. Rollback records are logged whenever a transaction is rolled back. Servers save enough space to log a rollback record for every update belonging to an open transaction. If a transaction completes successfully, no rollback records are logged, and the space reserved for them is released.
In long-running transactions, rollback records can reserve large amounts of space.
To check the space used by the syslogs, run the sp_spaceused:
sp_spaceused syslogs
The output is:
name total_pages free_pages used_pages reserved_pages --------------- --------------- --------------- --------------- -------------- syslogs 5632 1179 3783 670
The dbcc checktable(syslogs) produce a similar output as:
Checking syslogs: Logical pagesize is 2048 bytes The total number of data pages in this table is 3761. *** NOTICE: Space used on the log segment is 3783 pages (7.39 Mbytes), 67.17%. > *** NOTICE: Space reserved on the log segment is 670 pages (1.31 Mbytes), 11.90%. *** NOTICE: Space free on the log segment is 1179 pages (2.30 Mbytes), 20.93%.
If the last chance threshold for the transaction log fires when it seems to have sufficient space, it may be the space reserved for rollbacks that is causing the problem. See “Determining the current space for rollback records” for more information.
