DBCTL single-phase commit

A CCTL communicating with just one resource manager (IMS DBCTL subsystem) can request a sync point using just a single phase. If the CCTL communicates with more than one resource manager, it must use the two-phase commit process.

When the CCTL decides to commit a UOR, it can request a single-phase sync point. Single-phase commit can affect the recoverability of in-doubt data. A transaction is only in-doubt for the short time between the sync-point request and DBCTL’s commit. IMS can recover in-doubt data after a thread failure during single-phase commit, but cannot recover in-doubt data after a subsystem failure.