z/OS V1R6.0 DFSMS Access Method Services for Catalogs

DEFINE CLUSTERTo avoid potential failures with a modal command sequence in your IDCAMS job:vvSpecify the data set name instead of the DD name; orUse a separate job step to perform any sequence of commands (for example,REPRO, IMPORT, BLDINDEX, PRINT, or EXAMINE) that follow a DEFINEcommand.Recommendation: DB2 uses Access Method Services DEFINE CLUSTER forSTOGROUP defined data sets. This can result in performance problems forpartitioned table spaces if multiple partitions are defined on the same volume. DB2uses software striping on partitioned table spaces to improve performance ofsequential queries. The throughput is then gated by the data delivery capability ofeach volume. Since each partition is a separate data set, this problem can beavoided by allocating all the partitions in a single JCL step in an IEFBR14 (notIDCAMS) job. See z/OS DFSMS: Using Data Sets for details. Allocating all thepartitions in this manner works if there are adequate number of volumes availablewith the requested space quantity in a single SMS storage group to satisfy all thepartitions.Restriction: If you specify IMBED, KEYRANGE, ORDERED, or REPLICATE it willbe ignored.DEFINE CLUSTER ParametersThe DEFINE CLUSTER command uses the following parameters.Required ParametersCLUSTERCLUSTER defines or recatalogs a cluster or cluster entry.The CLUSTER keyword is followed by the parameters specified for the clusteras a whole. These parameters are enclosed in parentheses and, optionally, arefollowed by parameters given separately for the DATA and INDEXcomponents.Abbreviation: CLNAME(entryname)Defines the cluster’s entryname or the name of each of its components. Theentryname used for the cluster as a whole is not propagated to the cluster’scomponents.For SMS and non-SMS-managed clusters, the component names must resolveto the same catalog as the data set’s cluster name.You can define a separate entryname for the cluster, its data component, andits index component. If no name is specified for the data and indexcomponent, a name is generated. When the cluster, data component, and indexcomponent are individually named, each can be addressed. For information onsystem generated names, see z/OS DFSMS: Using Data Sets.When defining a VSAM volume data set (VVDS), the entryname for the clusteror the data component must be in the form SYS1.VVDS.Vvolser, where volumeserial number is the volume serial number specified by the VOLUMESparameter. The default primary and secondary allocation is 10 tracks. Forinformation on defining a VVDS see z/OS DFSMS: Managing Catalogs.CYLINDERS(primary[ secondary])KILOBYTES(primary[ secondary])|Chapter 14. DEFINE CLUSTER 147