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Data Control Interval Size z/OS DFSMS Using Data Sets SC23-6855-00 |
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You can either specify a data control interval size or default to a system-calculated control-interval size. If you do not specify a size, the system calculates a default value that best uses the space on the track for the average record size of spanned records or the maximum record size of nonspanned records. If a CONTROLINTERVALSIZE value is specified on the cluster level, this value propagates to the component level at which no CONTROLINTERVALSIZE value has been specified. Normally, a 4096-byte data control interval is reasonably good
regardless of the DASD device used, processing patterns, or the processor.
A linear data set requires a control interval size of 4096 to 32768
bytes in increments of 4096 bytes. However, there are some special
considerations that might affect this choice:
If you specify free space for a key-sequenced data set or variable-length RRDS, the system determines the number of bytes to be reserved for free space. For example, if control interval size is 4096, and the percentage of free space in a control interval has been defined as 20%, 819 bytes are reserved. Free space calculations drop the fractional value and use only the whole number. To find out what values are actually set in a defined data set, issue the access method services LISTCAT command. |
Copyright IBM Corporation 1990, 2014
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