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Creating a couple data set (CDS) z/OS UNIX System Services Planning GA32-0884-00 |
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The TYPE(BPXMCDS) couple data set (CDS) contains the sysplex-wide mount table and information about all participating systems, and all mounted file systems in the sysplex. To allocate and format a TYPE(BPXMCDS) CDS, customize and invoke the BPXISCDS sample job in SYS1.SAMPLIB. The job will create two couple data sets: one is the primary and the other is a backup that is referred to as the alternate. In BPXISCDS, you also specify the number of mount records that are supported by the CDS. Use of the CDS functions in the following manner:
Following is the sample JCL with comments. The statements in bold contain the values that you specify based on your environment. Place the primary and alternate couple data sets on separate volumes.
AMTRULES specifies the number of automount rules that can be supported by z/OS UNIX. It must be large enough to describe each automount-managed directory in your automount policy. The maximum value is 5000. Generally, each managed directory requires one AMTRULE, and each generic or specific rule for that managed directory requires one-half of an AMTRULE. For example, an automount policy consisting of two managed directories where the first managed directory contains a single generic rule and the second managed directory contains three specific rules would require a total of four AMTRULES. The first managed directory requires 1.5 AMTRULES and the second managed directory requires 2.5 AMTRULES. Rule: Automount mounts must be included in the MOUNTS value. The number of automount mounts is the expected number of concurrently mounted file systems using the automount facility. For example, you might have specified 1000 file systems to be automounted, but if you expect only 50 to be used concurrently, then factor these 50 into your MOUNTS value. For more information about setting up a z/OS system to run in a sysplex, see z/OS MVS Setting Up a Sysplex. The NUMBER(nnnn) specified for mounts and automount rules (a generic or specific entry in an automount map file) is directly linked to function performance and the size of the CDS. If maximum values are specified, the size of the CDS will increase accordingly and the performance level for reading and updating it will decline. Conversely, if the NUMBER values are too small, the function (for example, the number of mounts supported) would fail after the limit is reached. However, a new CDS can be formatted and switched in with larger values specified in NUMBER. To make the switch, issue the SETXCF COUPLE,PSWITCH command. The number of file systems required (factoring in an additional number to account for extra mounts), determines your minimum and maximum NUMBER value. After the CDS is created, it must be identified to XCF for use by z/OS UNIX. |
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