LOGR couple data set use considerations

See the topics on Format the LOGR couple data set and make it available to the sysplex and When the coupling facility survives the sysplex failurefor additional considerations on LOGR CDS and CF structure use.

If you are planning to activate a newly formatted LOGR CDS as part of the sysplex-wide IPL and this is the first IPL for the sysplex, then refer to the instructions in Format the LOGR couple data set and make it available to the sysplex.
If this is not the first IPL for the sysplex, and on the next sysplex-wide IPL you plan to continue to use a LOGR CDS (or a mirror copy of one) that had been the last one used for this sysplex, then ensure the COUPLExx parmlib member specifies the current LOGR CDS before performing the sysplex-wide IPL or respond accordingly to message IXC289D during the initial re-IPL. Refer to z/OS MVS System Messages, Vol 10 (IXC-IZP) for more details.
If this is not the first IPL for the sysplex, and on the next sysplex-wide IPL you are planning to activate a newly formatted LOGR CDS, then IBM® recommends you take additional steps prior to the sysplex-wide IPL. Cause all applications using the Coupling Facility structure based log streams to be disconnected and the structures used by Logger to be unallocated before re-IPLing.
Note: Partitioning all of the systems for a sysplex-wide IPL can leave the structures used by Logger still allocated with a FAILED-PERSISTENT connection. The goal for this case is to avoid having any structures used by Logger with FAILED-PERSISTENT connections.

A DISPLAY LOGGER,L command will show which log streams have connections to systems in the sysplex as well as naming any associated CF structure. The DISPLAY XCF,STR command will show which structures are allocated within the sysplex. You can then issue a DISPLAY XCF,STR,STRNAME=structname command for any structure that is still allocated by Logger. At the bottom of the command response is the connection status. You can issue SETXCF FORCE,CON,STRNAME=structname,CONNAME=IXGLOGR_xxxx to force all of the connections and deallocate a structure.
If this is not the first IPL for the sysplex, and on the next sysplex-wide IPL you plan to activate a LOGR CDS (or a mirror copy of one) that had been previously used but this LOGR CDS is not the last one used for the sysplex, then additional steps prior to the sysplex-wide IPL are required. Cause all applications using the Coupling Facility structure based log streams to be disconnected and the structures used by Logger to be unallocated before re-IPLing (refer to the actions in the previous bullet).
For this case, if after the sysplex-wide IPL any structures that Logger would use still have FAILED-PERSISTENT connections, then unpredictable results may occur. The problems can result in conflicts between the LOGR CDS state information for log stream resources and the state information that may also be kept in the CF structures. When the LOGR CDS log stream state information indicates there are no outstanding connections to the log stream, then the CF structure lists are cleared before Logger will allow the next log stream connection to complete. If the LOGR CDS log stream state information indicates there were outstanding (failed-persistent) connections to the log stream, then conflicts could exist between the LOGR CDS state data and any state data kept in the structure lists. The conflicting state data can lead to unpredictable results for Logger's use of the log stream or structure resources. For example, the log stream may become unusable, loss of data conditions, or log stream offload errors can result.