Recovery coordination

The records within a recoverable VSAM data set are protected resources. The application program, the resource manager, and the syncpoint manager work together to protect resources.

DFSMStvs builds on these components:

VSAM record-level sharing (RLS)
System logger
Recoverable resource management services (RRMS)

These three components work in concert to provide the three basic functions necessary for implementing transactional recovery:

Resource locking
This function provides serialized access to changed resources. VSAM RLS and DFSMStvs use a locking function based on a coupling facility, and the locking is done at the VSAM record level.
Resource recovery logging
This function enables a resource manager to keep a record of the changes that a transaction makes recoverable resources. The system logger is the service that is used to accomplish this task.
Two-phase commit and backout protocols
This function provides the services that ensure that a transaction appears as an atomic operation. It is the responsibility of two-phase commit and backout protocols to ensure that all of the changes made by a transaction are either committed or backed out. DFSMStvs uses the resource recovery services (RRS) provided by the MVS™ syncpoint manager to accomplish this task.