Every TCOMMIT command requests a flush of the journal data involved in that transaction to disk. This setting controls what happens at that point. The value n may be 1 or 0:
When 1 (true) TCOMMIT does not complete until the journal data write operation completes.
When 0 (false) TCOMMIT does not wait for the write operation to complete.
0 or 1. The default is 0.
On the page System Administration > Configuration > Additional Settings > Compatibility, in the SynchCommit row, select Edit. Choose true (selected) or false (cleared).