Disaster recovery facilities

This section looks at the various alternatives for achieving disaster recovery with CICS® and also looks at utilities that can aid the process.

MVS system logger recovery support

The MVS™ system logger provides support that enables a recovery resource manager to be associated with a log stream (that is, a local recovery resource manager operating on behalf of a remote site). The name of the recovery resource manager is specified when a new log stream definition is created or an existing log stream definition is updated. When a recovery resource manager connects to the log stream, through the IXGCONN service, it requests that a resource manager-owned exit be given control when specified events occur. When such an event occurs, the MVS system logger invokes the exit specified by the resource manager and passes it details of the event. It is then the responsibility of the recovery resource manager to transmit log records to a remote site.

The remote site needs to be able to import log streams transmitted by the recovery resource manager; this too is provided by MVS system logger services. Importation is the process whereby log blocks resident in one log stream (the source log stream) are created in (or copied into) another log stream (the target log stream) while maintaining (in the target log stream) the same MVS system logger-assigned log block id and GMT time stamp that is assigned to the source log stream. The result of a log stream import is a copy of the source log stream in the target log stream.

CICS VSAM Recovery QSAM copy

CICS VSAM Recovery (CICSVR) 2.3 provides a QSAM copy function that can copy MVS log streams to a QSAM data set. Copies of the QSAM data can be sent either electronically or physically to the remote site. On arrival at the remote site, you can use the MVS system logger import services to put the log records into an MVS system logger log stream. Alternatively, you can use CICSVR to perform forward recovery of a data set using the QSAM data directly.

Remote Recovery Data Facility support

The Remote Recovery Data Facility (RRDF) product from the E-Net Corporation supports the CICS log manager. RRDF Version 2 Release 1 uses the disaster recovery services (for export and import of log streams) provided by the MVS system logger. RRDF connects to a log stream at the local site where the resource manager exit is specified, to register its interest. The recovery manager is given control whenever writes or deletes occur. Typically, writes are intercepted for transmission to the remote site. Delete requests are intercepted to prevent CICS from deleting system log records before RRDF has sent them to the remote site. RRDF at the remote site receives the transmitted log records, establishes an import connection to a log stream, and imports the log records.

CICSVR 2.3 shadowing

CICSVR 2.3 provides a data shadowing facility. Shadowing helps to reduce recovery time by applying forward recovery logs periodically at the remote site. See CICSVR 2.3 documentation for a complete explanation.

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