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

DEFINE ALTERNATEINDEXSecondary amounts can be allocated on all volumes available to contain partsof the alternate index, regardless of the key ranges when the alternate index isextended.You can include the amount of space as a parameter of ALTERNATEINDEX, asa parameter of DATA, or as a parameter of both DATA and INDEX.vvIf the space is specified as a parameter of ALTERNATEINDEX, the amountspecified is divided between the data and index components. The divisionalgorithm is a function of control interval size, record size, device type, andother data set attributes.If the division results in an allocation for the data component that is not anintegral multiple of the required control area size, the data component’sallocation is rounded up to the next higher control area multiple. Thisrounding can result in a larger total allocation for your alternate index thanwhat you specified.If the space is specified as a parameter of DATA, the entire amount given isallocated to the data component. An additional amount of space, dependingon control interval size, record size, device type, and other data setattributes, is allocated to the index component.To determine the exact amount of space allocated to each component, list thealternate index’s catalog entry, using the LISTCAT command.The primary and each secondary allocation must be able to be satisfied withinfive extents; otherwise, your DEFINE or data set extension is unsuccessful.You can use these keywords for both SMS managed and non-SMS-manageddata sets.primaryAllocates the initial amount of space to the alternate index.secondaryAllocates the amount of space each time the alternate index extends, as asecondary extent. If the secondary space allocation is greater than 4.0gigabytes, it is reduced to an amount as close to 4.0 GB as possible,without going over. This is not true for extended addressability data sets,which have no such space limitation. When you use secondary, space forthe alternate index’s data and index components can be expanded to amaximum of 123 extents.Abbreviations: CYL, KB, MB, REC, and TRKVOLUMES(volser[ volser...])Specifies the volumes on which an alternate index’s components are to havespace. This parameter is not required if the cluster is modeled or if the clusteris SMS-managed. You can specify VOLUMES for SMS-managed data sets;however, the volumes specified might not be used and, in some cases, canresult in an error.For SMS-managed data sets, you can use up to 59 volumes. If the combinednumber of volumes for a cluster and its associated alternate indexes exceeds59, unpredictable results can occur.You can let SMS choose the volumes for SMS-managed data sets by coding an* for the volser with the VOLUMES parameter. If both user-specified andSMS-specified volumes are requested, the user-specified volser must be inputfirst in the command syntax. The default is one volume.130 z/OS V1R6.0 DFSMS Access Method Services for Catalogs