Although a catalog's VSAM share options are ignored when it is in RLS mode, they are still used when the catalog is quiesced from RLS use. Therefore, it is necessary to ensure that correct share options are specified. For example, a catalog to be shared across the sysplex in RLS mode needs to be defined with SHAREOPTIONS(3 4) so that it can continue to be shared across the sysplex correctly if it is ever switched out of RLS mode and back to either ECS mode or VVDS mode.

• It is recommended that prior to enabling catalogs in RLS mode, all systems in the sysplex (including pre z/OS® 2.1 systems) have enabled SMSVSAM. The SMSVAM address space must be available in a fallback situation in order to switch catalogs out of RLS mode. It is also recommended that all systems in the sysplex have migrated to z/OS 2.1 prior to implementing RLS for Catalog to prevent accidentally accessing a catalog from a release that does not support RLS mode. If a system that does not support RLS for catalogs must remain in the sysplex, be aware that if a catalog in RLS mode is ever RLS-quiesced for any reason, the non-RLS system could start accessing the catalog in either ECS or VVDS mode. In this case, you will need to explicitly close the catalog from the non-RLS system before enabling the catalog back to RLS mode.
• It is necessary to stop RLS mode for a catalog if access is needed by a system that does not support the RLS protocol. This can be temporarily accomplished by using the MODIFY CATALOG,RLSQUIESCE(catname) command. This does not nullify the LOG parameter, but does remove the catalog from RLS mode on all systems. It can only be returned to RLS mode by issuing a MODIFY CATALOG,RLSENABLE(catname) command. To switch all catalogs used by this system from RLS to non-RLS mode, issue MODIFY CATALOG,RLSQUIESCE,SYSTEM. To switch all RLS-eligible catalogs from non-RLS back to RLS mode, issue MODIFY CATALOG,RLSENABLE,SYSTEM.
• The RLSENABLE and RLSQUIESCE interfaces are intended for you to enable your catalogs to RLS mode and only fallback to non-RLS mode during an emergency. They are not intended to be used to switch a catalog back and forth between RLS and non-RLS on a regular basis.
• It is recommended that you dedicate a separate CF cache structure and lock structure for any catalog in RLS mode for better performance and failure isolation.
• To protect catalog’s integrity, the SYSIGGV2 BCS resource will be held share by each SMSVSAM address space while a catalog is opened for RLS access. This is done to ensure that applications that explicitly raise the ENQ exclusive in order to have the exclusive access to the catalog can no longer do so. The SYSIGGV2 BCS resource will be released when the catalog is closed for RLS access.
• If you plan to terminate the SMSVSAM address space for a long time, and your catalog requests cannot tolerate the prolonged down time, consider quiescing the catalogs from the RLS access before terminating the SMSVSAM address space. Otherwise, if the SMSVSAM address space is down, an IEC365D message will be displayed on the console to indicate that some catalog requests are still waiting for the SMSVSAM address space to be available. The catalog requests will be waiting on SYSZIGG5 BCS ENQ in the user’s address space as long as the SMSVSAM is not available. You may decide to ignore the message if the SMSVSAM address space is going to be available soon, or issue RLSQUIESCE to switch all catalogs used by this system out of RLS mode. In this case once the SMSVSAM address space is available, you may issue MODIFY, CATALOG,RLSENABLE,SYSTEM to switch all RLS-eligible catalogs back to RLS mode.
• During a catalog hang, it is essential to capture the dumps from CAS, SMSVSAM, and MASTER address spaces from all systems in the sysplex. Simply issue MODIFY CATALOG,TAKEDUMP(SYSPLEX) to capture all dumps. You may need to increase your dump data sets to accommodate the addition of dumps from the SMSVSAM address space and its dataspaces, especially if there are buffers placed above the bar.
• To identify which job(s) may be contributing to a catalog hang, use the combinations of the following console commands:

  MODIFY CATALOG,LIST 
  DISPLAY GRS,C 
  DISPLAY SMS,SMSVSAM,DIAG(CONTENTION)

  If a diagnosis is impossible, restart both the CAS and SMSVSAM address space from all involved systems.
• Although a catalog's VSAM share options are ignored when it is in RLS mode, they are still used when the catalog is quiesced from RLS use. Therefore, it is necessary to ensure that correct share options are specified. For example, a catalog to be shared across the sysplex in RLS mode needs to be defined with SHAREOPTIONS(3 4) so that it can continue to be shared across the sysplex correctly if it is ever switched out of RLS mode and back to either ECS mode or VVDS mode.