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

DEFINE ALTERNATEINDEXRECORDSIZE(average maximum|4086 32600)The average and maximum length, in bytes, of an alternate index record.An alternate index record can span control intervals, so RECORDSIZE can belarger than CONTROLINTERVALSIZE. The formula for the maximum recordsize of spanned records as calculated by VSAM is:MAXLRECL = CI/CA * (CISZ - 10)where:v MAXLRECL is the maximum spanned record sizev CI/CA represents the number of control intervals per control areav CA is the number of control areasv CISZ is the quantity control interval sizeYou can use either of the following formulas to determine the size of thealternate index record:vvWhen the alternate index supports a key-sequenced base cluster, use thisformula:RECSZ = 5 + AIXKL + (n x BCKL)When the alternate index supports an entry-sequenced base cluster, use thisformula:RECSZ = 5 + AIXKL + (n x 4)Variables in the formulas represent these values:vvvvvRECSZ is the average record size.AIXKL is the alternate-key length (see the KEYS parameter).BCKL is the base cluster’s prime-key length. (You can enter the LISTCATcommand to determine this base cluster’s prime-key length).n = 1 when UNIQUEKEY is specified (RECSZ is also the maximum recordsize).n = the number of data records in the base cluster that contain the samealternate-key value, when NONUNIQUEKEY is specified.When you use NONUNIQUEKEY, give a record size large enough to allow foras many key pointers or RBA pointers as you might need. The record lengthvalues apply only to the alternate index’s data component.Restriction: REPRO and EXPORT do not support data sets with record sizesgreater than 32760.REPLICATE|NOREPLICATEThe REPLICATE|NOREPLICATE parameter is no longer supported. If youspecify this parameter, VSAM ignores it, and no message is issued.REUSE|NOREUSEIndicates whether or not the alternate index can be used again as a newalternate index.REUSEIndicates that the alternate index can be used over again as a new alternateindex. When a reusable alternate index is opened, its high-used RBA canbe set to zero. Open it with an access control block using the RESETattribute.136 z/OS V1R6.0 DFSMS Access Method Services for Catalogs