The following open modes are available with the BTAM access method:
INOUT | Retrieve records from an existing file and add new records; no header labels are written, since the file must already exist. |
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 and the file is read backwards. Files which extend over several volumes can only be processed individually (with the aid of the VSEQ operand). |
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. |
The OPEN modes INPUT and REVERSE differ, at OPEN time, only in how the tape is positioned. An OPEN REVERSE followed by an RD or RDWT operation will not result in a reverse read.
BTAM operations and OPEN modes
BTAM operation | INPUT | REVERSE | OUTPUT | INOUT / OUTIN / SINOUT |
CHK | x | x | x | x |
Control * | n | n | x | x |
ERG | x | x | ||
RD/RDWT | x | x | x | |
REV/REVWT | x | x | x | |
RT/RTL | x | x | x | |
RNT/RNTL | x | x | x | |
WRT/WRTWT | x | x | ||
WT | x | x | x | x |
MINF | x | x | x | x |
POS | x | x | x | x |
RBID | x | x | x | x |
RDBF | x | x | ||
SYNC | x | x | x | x |
where:
x = n = * | permissible. output control functions are not permissible. “Control” stands for the operands FSF, BSF, WTM, RUN, ERG, FSR, BSR, REW. These are described in the chapter "BTAM - Process tape files (type S)". |