Joined: 14 Mar 2007 Posts: 8620 Location: Back in jolly old England

Posted: Wed Jul 22, 2009 3:57 pm Post subject:

What happened to your access to the IDCAMS manual ??? or google perhaps ???

Quote:

RECORDSIZE(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 be larger than CONTROLINTERVALSIZE. The formula for the maximum record size of spanned records as calculated by VSAM is:

MAXLRECL = CI/CA * (CISZ - 10)

where:

MAXLRECL is the maximum spanned record size
CI/CA represents the number of control intervals per control area
CA is the number of control areas
CISZ is the quantity control interval size

You can use either of the following formulas to determine the size of the alternate index record:

When the alternate index supports a key-sequenced base cluster, use this formula:

RECSZ = 5 + AIXKL + (n x BCKL)

When the alternate index supports an entry-sequenced base cluster, use this formula:

RECSZ = 5 + AIXKL + (n x 4)

Variables in the formulas represent these values:

RECSZ 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 LISTCAT command to determine this base cluster's prime-key length).

n = 1 when UNIQUEKEY is specified (RECSZ is also the maximum record size).

n = the number of data records in the base cluster that contain the same alternate-key value, when NONUNIQUEKEY is specified.

When you use NONUNIQUEKEY, give a record size large enough to allow for as many key pointers or RBA pointers as you might need. The record length values apply only to the alternate index's data component.

Restriction: REPRO and EXPORT do not support data sets with record sizes greater than 32760.

Joined: 06 Jun 2008 Posts: 8201 Location: Dubuque, Iowa, USA

Posted: Wed Jul 22, 2009 5:01 pm Post subject:

When defining an alternate index to a VSAM file, you must know whether or not the alternate index key is unique. If it is unique, the alternate index record size formula as quoted by expat reduces to 5 + primary key length + alternate index key length. If it is not unique, you must determine how many duplicates may occur -- either by knowing or by guessing -- and plug that number into the formula quoted by expat. In all cases, however, the alternate index record size has nothing to do with your base cluster record size.