Estimating the size of the root addressable area (HDAM or PHDAM only)
To estimate the size of the root addressable area, you can use a simple formula.
You can use the following formula to estimate the size
of the root addressable area:
(A x B) / C = D- A =
- the number of bytes of a database record to be stored in the root addressable area
- B =
- the expected number of database records
- C =
- the number of bytes available for data in each CI or block CI or block size, minus overhead)
- D =
- the size you will need, in blocks or CIs, for the root addressable area.
If you have specified free space for the database,
include it in your calculations for determining the size of the root
addressable area. Use the following formula to accomplish this step:
(D x E x G) / F = H- D =
- the size you calculated in the first formula (the necessary size of the root addressable area in block or CIs)
- E =
- how often you are leaving a block or CI in the database empty for free space (what you specified in the fbff operand in the DBD)
- F =
- (E-1) (fbff-1)
- G =
- 100 100 - fspf The fspf is the minimum percentage of each block or CI you are leaving as free space (what you specified in the fspf operand in the DBD)
- H =
- the total size you will need, in blocks or CIs
Specify the number of blocks or CIs you need in the root addressable area in the RMNAME=rbn keyword in the DBD statement in the DBD.