Unicenter CA MIM Resource Sharing Coupling Facility Structure System-Managed REBUILD Support

Document ID : KB000055932
Last Modified Date : 14/02/2018
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In Version 4.5 Service Pack 2, Unicenter CA MIM Resource Sharing (Unicenter CA MIM) has been enhanced to support system-managed REBUILD of Unicenter CA MIM control files residing on a coupling facility device. This enhancement improves the operational characteristics of coupling facility structure-based control files by eliminating the need for special Unicenter CA MIM procedures for performing coupling facility maintenance and reconfiguration activities. This feature is supported when Unicenter CA MIM is executing on an OS/390 2.10 or any z/OS operating system.

Note: this enhancement does not support, nor is it intended to support, a coupling facility structure rebuild in which a given structure is rebuilt in a newly allocated structure, using the IBM XES coordinated rebuild API.

Unicenter CA MIM exploitation of coupling facility structure-based control files was introduced in Version 4.3. At that time, support for a coupling facility structure rebuild event was unnecessary due to the inherent support within Unicenter CA MIM for control file migration as well as support for up to 100 unique control files. Although Unicenter CA MIM still has no need to support coupling facility structure rebuild for control file access and availability concerns, a need was recognized to provide installations with a means to react to coupling facility operational management events.

Unicenter CA MIM Version 4.5 added toleration for REBUILD operations directed to a given coupling facility. This was primarily directed towards an installation's need to quiesce the use of a given coupling facility in preparation for maintenance activity. Prior to Version 4.5 Service Pack 2, Unicenter CA MIM reacted to coupling facility structure REBUILD events by initiating an internal MIGRATE to an alternate control file (if necessary), then deleting the coupling facility structure control file that is the target of the REBUILD event. To re-allocate the target coupling facility structure control file, a Unicenter CA MIM ALLOCATE command had to be issued on each system in the MIMplex, followed by a single Unicenter CA MIM MIGRATE command if the target structure was to become the primary Unicenter CA MIM control file. This toleration support still required special procedures to make coupling facility structures available following a coupling facility maintenance event.

With Version 4.5 Service Pack 2 applied to all MIMplex systems, Unicenter CA MIM supports system-managed REBUILD of coupling facility structure control files. This means that Unicenter CA MIM continues to operate while the system-managed REBUILD process moves a coupling facility structure control file from one coupling facility to a new coupling facility. The operation can take place with a single z/OS SETXCF START,REBUILD command and does not require any special Unicenter CA MIM commands or procedures preceding or following the system-managed REBUILD operation.

Note that IBM coupling facility system-managed REBUILD is operator initiated for moving coupling facility structures and is not invoked for coupling facility hardware type failures. Unicenter CA MIM will continue to react to a coupling facility structure control file error condition by marking the active control file file "in-error" and initiating a control file migration to the next available backup control file.

Version 4.5 Service Pack 2 can be applied to one system at a time; a global shutdown of MIM is not required, however, support for system-managed structure REBUILD of Unicenter CA MIM control files will not be functional until Version 4.5 Service Pack 2 is applied to all systems in the MIMplex.

System-managed coupling facility structure REBUILD was introduced with OS/390 R8. For more information, refer to the IBM publication, Setting Up a Sysplex. In order for any coupling facility structure to be eligible for a system-managed REBUILD operation, several items must be true as defined by IBM:

  1. All systems in the sysplex must be at OS/390 R8 or higher.
  2. The CFRM couple data set must have been formatted using an OS/390 R8 or higher version of IXCL1DSU, the couple data set format utility, and a SMREBLD DATA ITEM must be specified at couple data set format time.
  3. The coupling facility structure must have been allocated by the initial connection from an OS/390 R8 or higher system.
  4. The CFRM policy for the coupling facility structure must specify more than one coupling facility name in the preference list.
  5. At least one other coupling facility, as defined in the coupling facility structure preference list CFRM policy, must be available at the time the system-managed coupling facility structure REBUILD operation is attempted.

The following example lists sampled CFRM format utility statements to define a CFRM couple data set that supports system-managed REBUILD. These statements are supplied as SYSIN to the IXCL1DSU utility:

DEFINEDS SYSPLEX(AORPLX01)     /* CFRM COUPLE DATA SET */
DSN(SYS1.AORPLX01.VMVXE13.CFRM)
VOLSER(MVXE13)
NOCATALOG
DATA TYPE(CFRM)
ITEM NAME(POLICY)  NUMBER(6)
ITEM NAME(CF)      NUMBER(8)
TEM NAME(STR)     NUMBER(128)
ITEM NAME(CONNECT) NUMBER(32)
ITEM NAME(SMREBLD) NUMBER(1)  /* OS390/R8 AND UP */

You can use the response from a D XCF,COUPLE,TYPE=CFRM command to determine whether a given CFRM couple data set has been formatted to include the SMREBLD data item and whether this data set is capable of supporting system-managed REBUILD operations.

You can use the response from a D XCF,STR,STRNM=control_file_name to determine whether the allocated structure can support a system-managed REBUILD by examining the coupling facility preference list as well as the system-managed REBUILD level of the named structure.

In an environment where Version 4.5 Service Pack 2 has not yet been applied to all MIMplex systems, Unicenter CA MIM will not react to a SETXCF REBUILD request, in effect, reverting back to the pre-Version 4.5 Service Pack 2 operational characteristics of coupling facility structure control files. In this mode of operation, to terminate use of a coupling facility structure control file, perform the following steps:

  1. Issue a MIGRATE command to an alternate control file if the coupling facility structure control file is the active IN-USE Unicenter CA MIM control file. The response from a Unicenter CA MIM DISPLAY FILES command shows the state of the control file.


  • Issue a Unicenter CA MIM DEALLOC XESFILEID=nn for the desired coupling facility structure control file. Again, the response from a Unicenter CA MIM DISPLAY FILES command can be used to determine the nn value for the DEALLOC command. The DEALLOC XESFILEID=nn must be issued on all active systems in the MIMplex.


  • Once all active MIMplex systems have deallocated the target coupling facility structure control file, issue the following command on any system in the sysplex to delete the structure from the coupling facility:
  • SETXCF FORCE,STR,STRNM=control_file_name.
  • When ready to use the coupling facility structure control file once again, issue the following Unicenter CA MIM command on all active MIMplex systems:
  • ALLOC XESFILEID=nn,STRNAME=control_file_name