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

Bit 5—No Record FoundIt should be determined if the file-data-check error bit (ISWEX bit 4) is also present. If itis present, any pertinent parameters (such as sector ID) should be saved and the operationretried. After 16 unsuccessful retries, the user should be notified.If the file-data-check error bit is not present, it should be determined if the missingaddress mark indicator (ISWEX bit 1) is present. If it is present, a recalibrate operationshould be performed and the original sequence of operations retried. After 16 unsuccessfulretries, the user should be notified.Verify that the heads are positioned over the desired track by executing the load andread next secto •ID sequence. Retry the original operation and notify the user after 16unsuccessful retries.Bit 6—Incorrect Length RecordThis condition may not be treated as an error by the system program, in which case norecovery procedure is recommended. If this condition is considered an error, however,the suggested procedure is to validate the DCB and retry the operation.Bit 8—Storage Data CheckRead the residual address from the subchannel address register. The command to do thisis an immediate read with a modifier of hex F (1111). The command can be used by theprogram to determine the contents of the data address register which is held and updatedby the 5022 subchannel. Use this address to determine what storage location had badparity and in which sector the error occurred. Validate that location and retry theoperation beginning with the sector where the error occurred. Another procedure wouldbe to validate the entire data table in storage and retry the operation in its entirety.Bit 9—Program CheckValidate the address of the DCB given on the start I/O command. If correct, validate theDCB by correcting the word count and/or the data address fields and retry the operation.Bit 14—Interface Data CheckRead the residual address to determine in which sector the error occurred. Validate theDCB and retry the operation five times. If unsuccessful, issue a halt I/O command to thedisk module, to reset the system, and retry once. If unsuccessful, assume that a hardfailure condition exists.Bit 15—Read ISWEXAny necessary parameters should be saved and the interrupt status word extension (ISWEX)should be read. If the ISWEX indicates a hardware error (bit 2 present), a halt I/O commandshould be issued to the module and then the original sequence of operations retried.After one unsuccessful retry, the user should be notified.Recovery from ISWEX ErrorsBit 0—File Data UnsafeA halt I/O command should be issued to the module and the original operation retried.After five unsuccessful retries, the user should be notified.Bit 1—Missing Address MarkIt should be verified that the disk has been initialized by reading the next sector ID on adifferent track or cylinder. If the disk has been initialized, an attempt should be made torestore the address mark by reformatting the original track with its original identifiers.Then, a sector ID should be read from the reformatted track. If unsuccessful, the usershould be notified that the track is defective.