Error Recovery Procedures - IBM 7074 General Information Manual

The following procedures form the basis of the error
recovery routines used in input-output programming
for
IBM
Programming Systems packages. For efficient
utilization of data processing systems, the use of these
procedures is recommended in writing input-output
routines.
Figure 14 shows the 7631-1301 error conditions that
can occur with 7000 series systems and specifies the
minimum action required. Data check errors should be
examined and handled before program check or excep-
tional condition errors.
The actions referred to in Figure 14 are:
Action 1
1. Repeat the operation once (for example, prepare
to verify and read or write. When a response check
occurs on a read, or a response check or a format
check occurs on a write or write check, the prepare to
verify is not required except on the
IBM
7090-94
System.
2. If the error condition persists, print message 1
(see below).
Action 2
1. Execute part 1 of action 1 as many as four times.
2. After a fifth error indication, recalibrate the ac-
cess mechanism with a seek to the outer customer
Sense Bit Assignment Assignment Comment
Status Bit BCD
Char. No. Bit
0 3
A Reserved Summary Byte
5 4 Program Check
6 2 Data Check
7 1 Exceptional Condition
1 3 A Invalid Sequence Program Check
5 4
Invalid Code Program Check
6 2 Format Check Program Check
7 1 No Record Found Program Check
2 3 A Invalid Address Program Check
5 4
Response Check Data Check
6 2 Data Compare Check Data Check
7 1 Parity or Check Char Code Check Data Check
Error Recovery Procedures
engineering track. Use 9@00 to 9@39 for the
seek address.
For the 7070-7074, the control command must spec-
ify two alpha order words for the seek. For example,
RDWC
-40 2-5 6-9, where 2-5 contains the address of
the first order word and 6-9 contains the address of
the second order word.
The two alpha order words are as follows:
First word:
a:
800x9 x = 0-9
( module number)
Second word:
a:
@xxOO xx=00-39
In two digit representation the order words appear
as follows:
a:
9890909x99
a:
469x9x9090
3. Seek to any track address. This moves the access
mechanism to cylinder zero.
4. Seek to the desired track.
5. Execute part 1 of action 1 as many as four times.
6. After a ninth error indication, print message 1.
NOTE:
In
IBM
1301
IOCS
routines, a no-record-found
condition causes an exit to the user. A return to the
lOCS
routine with the same record address causes ex-
ecution of a no-record-found error routine. The user
may have an overflow indication that must be inter-
rogated on the track that caused the no-record-found
indication.
When Encountered When Encountered When Encountered
During A During a Write or
During a Control
Read Operation
Write Check
Operation
Operation
Action 1 Action 1 Not applicable
Not applicable Not applicable Action 1
Not applicable Action 1 Not applicable
Action 2 Action 2 Not applicable
Action 4
Action 4 Not appl icable
Action 1 Action 1 Not applicable
Not applicable Action 3 Not applicable
Action 3 Action 3 Action 1
3 3
A
Access Inoperative
Exceptional Condition Action 1 Action 1 Action 1
5
4 Access Not Ready Exceptional Condition Action 1
Action 1 Action 1
6 2 1301 Circuit Check Exceptional Condition Action 1 Action 1 Action 1
7 1
7631 Circuit Check
Exceptional Condition Action 1 Action 1 Not applicable
Figure 14. Error Conditions and Actions Required
Error Recovery Procedures 21