z/OS DFSMS automatically allocates
buffers for storing input and output for a QSAM file above or below
the 16-MB line as appropriate for the file.
Most QSAM files have buffers allocated above the 16-MB line.
Exceptions are:
- Programs running in AMODE 24.
- Programs compiled with the DATA(24) and RENT options.
- Programs compiled with the NORENT and RMODE(24) options.
- Programs compiled with the NORENT and RMODE(AUTO) options.
- EXTERNAL files when the ALL31(OFF) runtime option is specified. To specify the ALL31(ON) runtime option, all programs in the run unit
must be capable of running in 31-bit addressing mode.
- Files allocated to the TSO terminal.
- A file with format-S (spanned) records, if the file is any of
the following:
- An EXTERNAL file (even if ALL31(ON) is specified)
- A file specified in a SAME RECORD AREA clause of the I-O-CONTROL paragraph
- A blocked file that is opened I-O and updated using the REWRITE statement