Use the following formula to calculate your initial coupling facility structure size:

structure size = (b × 4K) + (b/10 × 4K × n) + C

where:

b

is the number of I/O buffers defined in ICHRDSNT. (For backup data sets use 20% of the value specified for the primary).

4K

is the size of the buffer

b/10

is 10% of the total number of buffers per system, to allow different data reference patterns

n

is the number of CPCs in a sysplex

C

is the amount of storage required for coupling facility control information

For a 5-way sysplex with 255 I/O buffers, the primary structure size would be:

(255 × 4K) + (26 × 4K × 5) + C = 1540K + C

and the backup structure size would be:

(51 × 4K) + (5 × 4K × 5) + C = 304K + C