Setting up the logging environment

This topic outlines the tasks that you need to complete to set up the DFSMStvs logging environment correctly. These steps are in the order in which you should complete them. You might have completed some of the tasks in your planning phase.

Plan your DFSMStvs logging environment by gathering this information:
1. The number of DFSMStvs instances in your environment
2. The number of forward recovery logs that you require
3. The expected average buffer sizes and transaction rates in your environment
4. The number of coupling-facility structures that you require and their sizes
Ensure that you are authorized to use the MVS™ IXCMIAPU utility. This utility enables you to define, update, and delete entries in the LOGR couple data set.
Format and define the LOGR couple data set. You need to know how many log streams and structures that you are likely to need. Each DFSMStvs instance needs two system log streams. Optionally, you might want to have a log of logs and a number of forward recovery log streams.
Perform these steps:
1. Use the MVS IXCMIAPU utility to create the LOGR couple data set.
2. Define the LOGR couple data set to the sysplex and make it available.
Define coupling-facility structures in the CFRM policy couple data set.
Activate the LOGR subsystem.
Using RACF®, a component of the Security Server for z/OS, define RACF profiles in LOGSTRM classes so that DFSMStvs can access log streams.
Use the MVS IXCMIAPU utility to add information about log streams, log stream models, and coupling-facility structures to the LOGR couple data set.

Because DFSMStvs writes to forward recovery log streams, the space required for these log streams might increase. Similarly, because DFSMStvs writes to the primary and secondary system log streams (undo and shunt log streams), the demand increases for space in the coupling-facility structure. DFSMStvs moves long-running transactions and transactions that become shunted (due to backout failure) from the undo log stream to the shunt log stream.

The size of the coupling-facility structure for the primary log stream can affect performance. If the structure is too small, the system logger moves log buffers off to DASD spill data sets. While the system logger is moving log buffers, it is unable to service write requests from DFSMStvs.

Setting up DFSMStvs logging describes how to set up DFSMStvs logging.

Related reading: For more information about the utility, see z/OS MVS Setting Up a Sysplex.