MPE/iX Intrinsics Reference Manual (32650-90875)

256 Chapter6
Command Definitions (FLUSHLOG-GETUSERMODE)
FREADBACKWARD
If length is larger than the size of the logical record, and the multirecord
aoption in FOPEN/HPFOPEN was not specified, transfer is limited to the
length of the logical record. If the multirecord
aoption in
FOPEN/HPFOPEN is specified, transfer continues until either
length is
satisfied or end-of-data is encountered, and each transfer begins at the
start of the next physical record (block). Any data remaining in the last
physical record read is inaccessible.
Operation Notes
Three restrictions apply when using FREADBACKWARD:
• Used only with a magnetic tape drive with read-reverse capability.
• The magnetic tape drive must be located on an HP-IB system.
• The magnetic tape NOBUF must be accessed.
NOTE Magnetic tape devices with read-reverse capability are not supported. A call
to FREADBACKWARD results in an error (CCL (1)).
Not used for KSAM files.
Condition Codes
CCE (2) Request granted.
CCG (0) Request denied. The logical beginning-of-data was encountered. When
reading a labeled magnetic tape file that spans more than one volume,
CCG (0) is not returned when beginning-of-tape (BOT) is encountered.
CCG (0) is returned at actual beginning of file, with a transmission log of 0
if an attempt is made to read past beginning-of-file.
CCL (1) Request denied. The information was not read because a tape error
occurred, or a tape error was recovered and the FSETMODE option was
enabled. Check the condition code in both normal I/O and nowait I/O.
Related Information
Manual Accessing Files Programmer's Guide