Step 5. Determine the amount of space needed for bitmaps

To calculate the number of bytes needed for bitmaps in your database, you can use the following formula:

A = D / ((B - C) x 8)

Where the values are:

A

The number of bitmap blocks or CIs you need for the database.

B

The CI or block size you have specified, in bytes, minus 4.

Four is subtracted from the CI or block size because each CI or block has a 4-byte FSEAP.

C

The number of RAPs you specified for a CI or block, times 4.

The number of RAPs is multiplied by 4 because each RAP is four bytes long. (B - C) is multiplied by 8 in the formula to arrive at the total number of bits that will be available in the CI or block for the bitmap.

D

The number of CIs or blocks in your database.

You need to add the number of CIs or blocks needed for bitmaps to your space calculations.