Control field values for spanned key-sequenced and entry-sequenced data sets

A control interval that contains the record segment of a spanned record contains no other data; it always has two RDFs. The possible hexadecimal values in their control fields follow.

Left RDF	Right RDF	Description
X'18'	X'50'	The right RDF gives the length of the first segment of a spanned record. The left RDF gives the update number of the segment.
X'28'	X'60'	The right RDF gives the length of the last segment of a spanned record. The left RDF gives the update number of the segment.
X'38'	X'70'	The right RDF gives the length of an intermediate segment of a spanned record. The left RDF gives the update number of the segment.

Figure 1 shows contents of the CIDF and RDFs for a spanned record with a length of 1306 bytes.

Figure 1. Format of Control Information for Spanned Records

There are three 512-byte control intervals that contain the segments of the record. The number "n" in RDF2 is the update number. Only the control interval that contains the last segment of a spanned record can have free space. Each of the other segments uses all but the last 10 bytes of a control interval.

In a key-sequenced data set, the control intervals might not be contiguous or in the same order as the segments (for example, the RBA of the second segment can be lower than the RBA of the first segment).

All the segments of a spanned record must be in the same control area. When a control area does not have enough control intervals available for a spanned record, the entire record is stored in a new control area.