Tape capacity considerations

Any IBM tape device supported by your operating system can be used for work space. However, using tape devices for work data sets rather than disk causes significant performance degradation and should, therefore, be avoided.

Three different tape work data set techniques are available to DFSORT: Balanced, Polyphase, and Oscillating. For information on how to calculate their requirements, see Table 1.

Note: The value you obtain for "min" is literally a minimum value; if, for example, your input uses a more efficient blocking factor than DFSORT or is spanned, you need more work space. Space requirements are also summarized in Table 1. DFSORT selects the most appropriate tape technique using these criteria.

Table 1. Work Space Requirements of the Various Tape Techniques
Work Space Requirements of the Various Tape TechniquesTape Technique	Maximum Input	Work Space Areas Required	Max. No. of Work Areas	Comments
Balanced tape (BALN)	15 volumes	Min=2(V+1)* tape units	32 volumes	Used if more than three work storage tapes are provided and file size is not given.
Polyphase tape (POLY)	1 volume	Min=3 tape units	17 volumes	Used if three work storage tapes are provided.
Oscillating tape (OSCL)	15 volumes	Min=V+2* or 4 tape units, whichever is greater	17 volumes	File size must be given. The tape drive containing SORTIN cannot be used as a work unit.
Note: V = Number of input volumes. Number of input volumes of blocking equals work space blocking.