IBM System/7 Functional Characteristics - All about the IBM 1130 ...

Operation Description14. Seek Seek to the alternate track.15. Format track Write sector identifiers on the alternate track with the flagbits set to 0 and 1, respectively, and the same cylinder andsector values that were originally in the defective track.16. Continue Proceed with initialization on the next track. (Return tostep 7 or step 10.)The basic requirement is for one pass through steps 1 to 8. An option must be providedto allow additional testing so that a track can be positively identified as good or defective.After initialization, only two types of programs should change track flags: (1) initializationprograms, which must be able to ignore all previously flagged tracks and unconditionallyflag or unflag any individual track; and (2) operating programs that can dynamicallyflag a track must perform steps 11 through 15 of this procedure.SUGGESTED RECOVERY PROCEDURESError or exception conditions are indicated by bits that are set in the device status word(DSW), the interrupt status word (ISW), and the interrupt status word extension(ISWEX) for the disk storage module. Minimum error recovery procedures are definedfor the disk storage module in the following discussions.Recovery from DSW ErrorsA condition that sets DSW bit 4 can be checked for recovery by first reading the ISWEXand checking for the presence of the unsafe bit (bit 0). If no unsafe condition exists (bit0 = 0), the disk file drive has not completed its starting sequence.If an unsafe condition does exist, a halt I/O command should be issued to reset the conditionsand the original operation retried. If the unsafe condition cannot be reset afterfive attempts, operator intervention is required.Recovery procedures for DSW bits 1 and 14 are described in Chapter 4 under "DeviceStatus Word," since these status conditions are defined for all I/O modules.Recovery from ISW Error or ExceptionBit 2—OverrunIf the overrun condition occurred while executing a write sequence, any pertinent parameters(such as word count) should be saved and the original sequence of operations retried.After eight unsuccessful retries, the user should be notified.If the overrun condition occurred while executing a read sequence, any pertinent parameters(such as word count) should be saved and the original sequence of operations retried.After 16 unsuccessful retries, the user should be notified.Bit 4—Drive Became Not ReadyIt should be determined if an unsafe condition exists (ISWEX bit 0 present). If this conditiondoes exist, a halt I/O command should be issued to reset the unsafe condition(s) andthe original operation retried. After five unsuccessful retries, the user should be notified.If no unsafe condition exists, the user should be notified to restart the file.IBM 5022 Disk Storage Module 15-29