If you cannot perform this test with actual queries, you can calculate a rough estimate for operational query requirements. Requirements for each retrieval vary considerably. Generally, this estimate uses the following fixed factors:
This estimate also uses the following variables:
The memory used for dynamically calculated values, which is based on the following numbers:
The number of blocks specified by the SET LOCKBLOCK command.
The number of cells in a logical block, which includes Dynamic Calc members. See value MH in Table 250, Worksheet: Estimating Memory Requirements for a Database.
The size of the data cache. See Sizing the Data Cache.
If direct I/O is used, the size of the data file cache. See Sizing the Data File Cache.
You can then use the following two calculations for the memory needed for retrievals:
Buffer and work area used in each retrieval:
retrieval buffer (10,240 bytes) + retrieval sort buffer (20,480 bytes) + formatting buffer (144,000 bytes) + each selected member in the retrieval (40 bytes) + each member of the largest dimension (8 bytes) + dynamic calc area + data cache size + data file cache size
Memory needed for estimated number of concurrent retrievals:
Member storage area for the largest dimension + (number of retrievals * sum of buffer and work areas used in each retrieval)
Summarize the calculations and write the result, in bytes, to the cell labeled ME in Table 250, Worksheet: Estimating Memory Requirements for a Database.
To estimate the maximum memory needed for concurrent queries, assume the following values for this example:
The area required by the largest dimension:
23,000 members * 8 bytes/member = 184,000 bytes
The number of selected members is generalized across all queries to be 10,000 members. The approximate memory requirement equals the following:
10000 members * 40 bytes/member = 400,000 bytes
Estimated memory for retrievals:
184,000 bytes + (20 concurrent inquiries * (10,240 bytes + 20,480 bytes + 144,000 bytes + 761,600 bytes + 3,145,728 bytes + 400,000 bytes)) = 75,824,960 bytes