There are a number of steps you must complete to generate
XCF/MRO support.
Procedure
- Ensure that the version of DFHIRP in the extended link
pack area (ELPA) is at the required level for all the MVS images containing
CICS systems to be linked.
Depending on the versions of
CICS installed in the MVS images participating in XCF/MRO, the versions
of DFHIRP installed in the images can be different. The DFHIRP module
must be from the most current CICS release in the image, or higher.
The CICS® TS for z/OS®, Version 5.4 DFHIRP
module, which is required for multiple XCF group support, can be used
only with z/OS, Version 2 Release 1 or
later.
- Ensure that each CICS APPLID is unique within the sysplex.
- Ensure that the value of the MAXMEMBER MVS
parameter, used to define the XCF couple data sets, is high enough
to cater for the largest CICS XCF group.
The maximum size
of any XCF group within a sysplex is limited by this value. The theoretical
maximum size of any XCF group is 2047 members.
External CICS interface
(EXCI) users that use an XCF/MRO link also join an XCF group. You
must therefore set the value of MAXMEMBER high
enough to allow all CICS regions and EXCI XCF/MRO users in the largest
CICS XCF group to join the group concurrently.
To
list the CICS regions and EXCI users in an XCF group, use the MVS DISPLAY command.
For example, to list the CICS regions and EXCI users in the DFHIR001
XCF group, use the command:
DISPLAY XCF,GROUP,DFHIR001,ALL
Do
not rely on the default value of MAXMEMBER, which
might be too low to allow all the CICS regions and EXCI users in the
largest XCF group to join the group. This is especially important
if you have only a few CICS XCF groups.
Likewise, do not set
a value much larger than you need, because this results in large couple
data sets for XCF. The larger the data set, the longer it takes to
locate entries.
Make the value of MAXMEMBER 10-15
greater than the combined number of CICS regions and EXCI users in
the largest CICS XCF group.
Results
Each CICS region joins an XCF group when it logs on to
DFHIRP. Its member name is its APPLID (NETNAME) used for MRO partners.
The XCF group name is specified on the XCFGROUP system
initialization parameter. If XCFGROUP is not
specified, the XCF group name defaults to DFHIR000.
At connect
time, CICS invokes the IXCQUERY macro to determine whether the CICS
region being connected to resides in the same MVS image. If it does,
CICS uses IRC or XM as the MRO access method, as defined in the connection
definition. If the partner resides in a different MVS image, CICS
uses XCF as the access method, regardless of the access method defined
in the connection definition.
CICS regions can use MRO or XCF/MRO
to communicate only with regions in the same XCF group. Members of
different XCF groups cannot communicate using MRO, or XCF/MRO, even
if they are in the same MVS image.