When spanned records span volumes, reading errors could occur when using QSAM, if a volume that begins with a middle or last segment is mounted first or if an FEOV macro is issued followed by another GET. QSAM cannot begin reading from the middle of the record. The errors include duplicate records, program checks in the user's program, and nonvalid input from the spanned record data set.
A logical record spanning three or more volumes cannot be processed in update mode (as described in Controlling Buffers) by QSAM. For blocked records, a block can contain a combination of records and record segments, but not multiple segments of the same record unless the program is using LBI. When records are added to or deleted from a data set, or when the data set is processed again with different block size or record size parameters, the record segmenting changes.
When QSAM opens a spanned record data set in UPDAT mode, it uses the logical record interface (LRI) to assemble all segments of the spanned record into a single, logical input record, and to disassemble a single logical record into multiple segments for output data blocks. A record area must be provided by using the BUILDRCD macro or by specifying BFTEK=A in the DCB.
When you specify BFTEK=A, the open routine provides a record area equal to the LRECL specification, which should be the maximum length in bytes. (An LRECL=0 is not valid.)