Example of an RSR complex

The following figure illustrates some of the concepts introduced in this topic, and shows what an RSR complex with XRF and data sharing might look like.

Figure 1. Example of an RSR complex with XRF and data sharing

Two active IMS systems share databases and a coupling facility. Each active IMS has its own alternate IMS. A single Tracking IMS tracks both active IMS systems.

The IMS™ logs are sent from the active IMS systems as they are created. This RSR complex uses XRF and data sharing. The active site has two active IMS systems, A and B, which are configured with XRF and data sharing. Each IMS has it's own logs, but both IMS systems share a master database, a RECON data set, and a coupling facility, which includes message queues and other structures. The remote site contains one tracking IMS that is used for storing log data received from the active IMS systems. All IMS systems in the RSR complex are configured with Transport Manager Subsystems (TMSs).

If one of the active site IMS systems is disrupted, you should use its XRF alternate IMS to take over its processing. If both IMS systems at the active site are disrupted, this setup is designed on the assumption that you are willing to recover both IMS systems, A and B, on the tracking IMS.

When updates are made to an active IMS, this IMS writes log data to an online log data set (OLDS), or, for batch, to a system log data set (SLDS). At the same time as the disk write, the active IMS also sends this log data to the tracking IMS. The tracking IMS stores this data in SLDS.

At the remote site, DBRC maintains log and database recovery information for the tracking IMS. The RECON data set of the tracking IMS is not a mirror of the RECON data set at the active site. DBRC records log data received from both active IMS systems and maintains database recovery information for the tracking IMS in the RECON data set of the tracking IMS.

RSR does not support active application processing against the shadow databases until a remote takeover of active processing occurs. At that point, the remote site becomes the new active site and you can restart the active IMS systems at that site. If the active IMS participates in data sharing, you need to switch all sharing IMS systems (the entire service group) to the remote site on an RSR takeover.