IMS has many features that provide high availability and complete recovery of the IMS system in all operating environments. The major features are:
This chapter describes XRF and RSR. For more information about IMS in a Parallel Sysplex environment, see Part VI, "IMS in a Parallel Sysplex Environment," on page 465. XRF and RSR are two features of IMS that can, optionally, be used to increase the availability of IMS systems and the data in IMS databases. Both rely on duplicating IMS subsystems and data on another z/OS system. The first of these is the XRF. The XRF functions are delivered as an integral part of IMS and are intended to provide increased availability of IMS subsystems. There is an overhead, both in machine usage and support, in using XRF. However, if you have an application that can only tolerate minimal outages, then you might consider using XRF. The second of these features is RSR. RSR is a separately priced component available with IMS. It provides similar facilities to XRF, but with some differences. Both features rely on having another IMS subsystem, situated on another z/OS system, that tracks the update activity of the primary IMS subsystem (only one for XRF, one or more for RSR) to provide a backup. The differences between the two features are discussed in "Comparison of XRF and RSR" on page 441. In This Chapter:
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