Opening a BTAM file

Opening a BTAM file depends on the OPEN mode. The table below provides an overview of the various modes and the resulting possibilities for processing a BTAM file.

OPEN mode	Processing
INOUT	Retrieve records from an existing file and add new records; no header labels are written, since it is assumed that the file already exists.
INPUT	Retrieve files from an existing file in the forward direction.
OUTIN	Create a new file and/or retrieve records; labels are written since a new file is being created.
OUTPUT	Create a new file.
REVERSE	As for INPUT, but the tape is positioned to EOF at OPEN time. Files which extend over several volumes can only be processed individually (with the help of the VSEQ operand in the FILE macro or the VOL-SEQUENCE-NUMBER operand in the ADD-FILE-LINK command).
SINOUT	As for INOUT, but the tape is not positioned; this is not permitted if the tape is positioned at the beginning of the tape.

Table 42: OPEN modes for BTAM files

The OPEN modes INPUT and REVERSE differ, at OPEN time, only in how the tape is positioned. An OPEN REVERSE followed by a RD or RDWT operation will not result in a reverse read.