Calculating primary record specification

A simple calculation of the estimated number of transactions per day multiplied by the maximum number of days provides the general size. This calculation corresponds to the formula:

CMRDETL Size = (transactions per day) x (number of days)

If you are using a single CMRDETL data set, it must be large enough to contain data for all the days that you want to preserve, which means that the primary record specification should be equal to the CMRDETL size by using the above formula.

If you are using dual CMRDETL data sets, the CMRDETL size can be distributed between the individual data sets.

Although VSAM allocates space according to the specified number of records, other factors such as the method of loading records and differences in the compressed size of the T6E records will affect the ability of VSAM to completely use all of a given control area. It is a good idea to increase the primary record specification by 25%.

For optimum VSAM performance, the primary allocation for CMRDETL should never be less than one cylinder.

The secondary extent should always be zero.