The value of the commit identifier, commid in the spt_committab table, becomes a random value (between 1 and 2,147,483,647 (231-1), instead of a monotonically increasing value. This reduces page lock contention on the row where the maximum commid resides when several distributed transactions try to insert an entry into the spt_committab table. spt_committab continues to have a unique, clustered index.
For information on how to configure Adaptive Server for two-phase commit functionality, see the Adaptive Server configuration documentation for your platform.
