NetMaster Database Administration › How to Create an NDB › Calculate Record Length

Calculate Record Length

Calculate the average and maximum record lengths as follows:

Average Record Length:

• Greater than the VSAM key length
• The approximate size of a stored data record. A stored data record needs:
  • KL (from above) +10 +
  • 3 times number of present fields +
  • 4 times number of present numeric fields +
  • 3 times number of present date or cdate fields +
  • 8 times number of present floating point or timestamp fields +
  • 5 times number of present time fields +
  • Total number of characters in present hexadecimal fields / 2
  • Number of characters in present character fields (less trailing blanks) +

Note: A data record can span multiple VSAM records. If there are some records in your design that can be very large, but most are short, calculate the sizes using most common record structure.

Maximum Record Length:

• A maximum of 274 + 2 times the VSAM key length
• Average record length (calculated above) + VSAM key length + 6

VSAM requires the maximum record length to be less than the data CI size less 7. Use a figure that leaves minimum wastage in a CI.

The only VSAM records in an NDB that have the maximum VSAM record length are the NDB transaction data records. These are inserted during processing of the NDB CREATE command.

Example: VSAM Definition

This example of a definition is a good starting point for your own definitions.

DELETE clustername CL
DEFINE  CLUSTER(NAME(clustername)   -
        VOL(volume)                 -
        INDEXED-
        SHAREOPTION(2 3) -
        DATA (NAME(dataname)-
        KEYS(60 0)-
        CISZ(4096)-
        RECSZ(200 1020)-
        FSPC(20 20))-
        INDEX (NAME(indexname)-
        CISZ(2048))