# Creating and sizing the 64-bit storage pool

Creating the 64-bit storage pool is a system definition task. Before you can specify an appropriate size on the ACBIN64 parameter in the DFSDFxxx member of the IMS PROCLIB data set, you must perform some calculations.

You can make your calculations based either on DASD allocation
or on the sizes of the 31-bit non-resident pool sizes.

The following are some examples:

- The current DASD space allocation for all the non-resident PSBs and non-resident DMBs in the ACB library is 2150 cylinders on a 3390-9, which is approximately 1.9 GB of DASD space. To have sufficient space to include as many ACB members as possible in the 64-bit pool, specify ACBIN64=2.
- There are 57 000 ACB members in the ACBLIB data set. The cumulative size of these ACB members is approximately 850 MB. The size of the non-resident DMB pool is 250 MB. The size of the non-resident PSB pool is 300 MB. Therefore, specify ACBIN64=1.