FastSort Manual

Sorting Interactively

FastSort Manual—429834-003

2-11

Controlling Extended Memory

By default, FastSort tries to use enough extended memory to make at most one merge

pass, depending on the size of the output file. You can specify the maximum amount of

extended memory FastSort can use with the parameters of the RUN command or with

SORT DEFINEs:

The maximum extended segment size for sorting depends on whether the VLM option

is on or off. For more information about this option, see Using VLM on page 9-10. To

use VLM for interactive sort operations, you must set up a SORT DEFINE. For more

information about SORT DEFINEs, see Section 7, Using SORT and SUBSORT

DEFINEs.

In addition to the parameters shown above, the amount of memory FastSort uses for

sorting input records depends on:



File size (f) in bytes, which is the total input record count times the maximum

output record length (for a permutation sort, the record length is the key length)



Scratch block size (b)



The amount of physical memory (m) not locked down when SORTPROG begins

The formula for determining the approximate amount of memory FastSort needs to

make no intermediate merge passes or only one intermediate merge pass is:

Table 2-1 on page 2-12 lists the specific formulas for RUN command parameters that

control extended memory. You can use the formulas to determine which parameter

makes the most efficient use of your resources to sort your input records.

Parameter Maximum Physical Memory FastSort Uses

MINSPACE 256 pages

AUTOMATIC 50 percent *

MINTIME 70 percent *

SEGMENT n n pages to a maximum of 32,767 pages

If VLM is on, the maximum SEGMENT size is 62,255 pages.

* Percentage of processor memory that is not locked down when SORTPROG begins.

MIN

bf

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