Operator Messages; Action Requirements; Terminal Action La (With Operator Option); Terminal Action Lb (Without Operator Option) - IBM 3803 Manual

Tape Cleaner Sequence
Operator Messages
Action Requirements
A tape cleaner sequence moves tape back and forth past the tape cleaner blade
to dislodge any contaminants that m.ay be causing read errors. The tape cleaner
sequence for a forward read operation is five backspaces, then four forward
spaces. For a backward read operation, the sequence is four backspaces, then
five forward spaces.
Beginning of Tape: If the beginning of tape (load point) is reached in "n"
backspaces during a tape cleaner sequence, reposition tape for a Forward Read
with "n minus 2" Forward Spaces. Reposition tape for a Backward_ Read with
"n" Forward Spaces.
Tape Mark Block: If a tape m.ark is read during a tape cleaner sequence, ignore
the unit exception indication and process the tape m.ark as a norm.al block.
An operator message m.ust include: ·
l. Message code.
2. Channel, tape control, and device addresses.
3. Comm.and in progress when error occurred.
4. Error condition causing the message.
5. All status and sense bits.
/ Terminal Action la (With Operator Option)
An operating system. m.ay provide operator-control options and/ or additional
program.med error recovery.
If both are defined:
1. Again attempt the recovery procedure.
2. Continue to the additional program.med error recovery.
Terminal Action lb (Without Operator Option)
Action II (Unit' Check)
If the additional program.med error recovery is defined, exit to it.
Move
csw
information to a work area, issue a sense comm.and (unless already
performed), and continue checking as in Figure 11.
Action Ill (Intervention Required)
No Device End in Unit Status: Test for
TU
Status B (sense byte 1; bit 2). If
TU
Status B is off, device is "nonexistenL" Provide operator message, post
completion with error condition, and exit to operating system.. See "Terminal
Action Ia.''
If
TU
Status B is on, the device is 'not ready.' Provide "operator intervention
required" message, and reissue the comm.and when the tape unit has been m.ade
ready.
Device End in Unit Status: If the comm.and was Rewind/Unload, continue
processing. Otherwise, ignore an intervention required condition, and continue
checking as indicated in Figure 11.
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3803-2/3420 Subsystem Description