SORT can operate in four different modes: disk-only, tape-only, integrated tape and disk, or memory-only.
The combination of disk size and number of tapes determines the sort mode as shown in Determining SORT Operating Mode.
Table 71. Determining SORT Operating Mode
|
Number of Tapes |
Disk Size |
Mode |
|---|---|---|
|
Not = 0 |
0 |
Tape-only |
|
Not = 0 |
Not = 0 |
ITD |
|
0 |
Not = 0 |
Disk-only |
|
0 |
0 |
Memory-only |
The following text identifies important characteristics of various SORT modes. The SORT modes are then described in detail.
Disk-only mode
The following are characteristics of disk-only sorting mode:
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Disk-only is generally faster than tape-only mode.
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A disk is the most reliable peripheral device.
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Less operator intervention is required than when you use tape-only mode.
-
The sort operation is limited by disk resources.
Tape-only mode
The following are characteristics of tape-only sorting mode:
-
The input file can be an indefinite length.
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A particular machine configuration is required—that is, you need several tape drives that must be capable of performing backward reads.
ITD mode
The following are characteristics of ITD sorting mode:
-
The disk develops longer strings on tape.
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The input file can be an indefinite length.
Memory-only mode
The following are characteristics of memory-only sorting mode:
-
Memory-only is generally the fastest mode.
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Memory-only is the mode least likely to encounter I/O problems.
-
Memory-only mode is limited to the amount of data it can sort:
-
It can sort a large number of small records
-
It can sort a small number of large records
-
It cannot sort a large number of large records
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