Function
Frees a basic peripheral which has a document loaded on it, or rewinds the magnetic tape on a specified deck and frees the deck, provided that the tape is not on-line to a user, or is in use by the system.
The command may also be used to carry out the operation on all tape decks whose tapes are not on-line to users or in use by the system.
It can also be used to terminate a LABEL or REDON command.
Format
Forbidden contexts
NOT OPERATOR
Execution
If the operator's number of a basic peripheral is given and the peripheral is not on-line to an object program, the peripheral is disengaged and the name of the document that is loaded on it is removed from :SYSTEM.DOCUMENT.
If the operator's number of a magnetic tape deck is given, the tape on the deck is rewound, provided that it is not on-line to a user. All information concerning the association between the deck and the tape is erased, and the deck is thus freed for the loading of another tape.
In the event of the command terminating successfully the operator is
informed by the message
UNIT number FREE
to which, for magnetic tape, will be appended
:-MT tsn FAILS m REPEATS
n
or in the case of non-standard tapes
:-NONSTANDARD TAPE FAILS m REPEATS
n
(The appended portion of the message will be suppressed if m
and n are zero.
If the facility to 'unload all tapes' is being used the message
becomes
UNITS a,b,c,...,n FREE
or
NO UNITS UNLOADABLE
The message for single tapes will then be output for all tapes for which
m and n are non-zero.
Example
UNLOAD 33
Error Messages
UNIT z IS NOT ENGAGED
UNIT z IS NOT IN REQUIRED STATE
UNIT z IS WRONGED
z IS AN ILLEGAL GEOGRAPHICAL NUMBER
UNIT z:- MT tsn IS IN USE BY THE SYSTEM
UNIT z:- MT tsn IS ONLINE TO JOB NUMBER n