Resource recovery programs

Three programs work together to protect resources:

Application program: The application program accesses protected resources and requests changes to the resources.
Resource manager: A resource manager is an authorized program that controls and manages access to a resource. A resource manager provides interfaces that allow the application program to read and change a protected resource. The resource manager also takes actions that commit or back out changes to a resource it manages.
Often an application changes more than one protected resource, so that more than one resource manager is involved.
A resource manager may be an IBM® product, part of an IBM product, or a product from another vendor. A resource manager can be:
- A database manager, such as DB2®
- A program, such as IMS/ESA® Transaction Manager, that accepts work from an end user or another system and manages that work
Note: The resource manager in resource recovery is different from an RTM resource manager, which is related to the operating system's recovery termination management (RTM) and runs during termination processing.
Sync-point manager: The sync-point manager coordinates changes to protected resources, so that all changes are made or no changes are made. The z/OS sync-point manager is recoverable resource management services (RRMS). Three MVS™ components provide RRMS function; because resource recovery services (RRS) provides the sync-point services, most technical information uses RRS rather than RRMS.
If your resources are distributed, so that they are on multiple systems, the communication resource manager on one system will coordinate the changes. Each communication resource manager works with RRS on its system.

RRS can enable resource recovery on a single system or, with APPC/MVS, on multiple systems.

The application program, resource manager, and sync-point manager use a two-phase commit protocol to protect resources.