User's Manual

XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL 14-1
14. 14Undefined tapes
To process tapes with labels that are not specifically defined in any
of the other chapters of this manual, the user may specify undefined
host and undefined labels. Labels are identified by virtue of their
length. Minimum and maximum unpacked label lengths can be
specified using the MAXLAB and MINLAB options on the VOLUME
command. If unspecified, label length defaults to include records of
80 to 81 bytes. The operating system software groups together any
combination of label records and their surrounding tape marks at the
beginning of a file. Since these labels are not otherwise defined,
there is no additional checking or use of their contents (other than the
JDE-selected option of printing them).
Unpacking of data and labels may be specified. If unpacking is
specified for the labels, the data must also require the same
unpacking method. The labels do not have to be unpacked even
though the data may require unpacking, if the MINLAB/MAXLAB
parameters are specified properly for the unpacked length.
The data tape blocks must be definable by the JDE parameters of the
BLOCK and RECORD commands.
Note: It should be noted that any data block that is the same length
as a label block is treated as a label; 80 is the minimum and 81 is the
maximum default label size
File format
A file under this system has the following characteristics:
• A file starts at the initial tape position and includes any labels or
single tape marks which precede the first data record. The file
ends on the last data record preceding a tape mark or label
record.
• Since a label record or a tape mark is used to terminate a file,
trailer labels for a given file are considered to be header labels
for the following file, if any.
At the end of processing of a file, the tape is positioned prior to
the tape mark or label record which caused termination of the
file processing. Thus, in the event that a file is terminated by a
single tape mark or a label without any following tape marks,
the preceding file is properly processed and any tape-related
errors (timeout, unreadable block, etc.) do not occur until the
operator starts processing on the nonexistent file.
• At the end of processing of a file, the tape is positioned prior to
the tape mark or label record which caused termination of the
file processing. Thus, in the event that a file is terminated by a
single tape mark or a label without any following tape marks,
the preceding file is properly processed and any tape-related