Date: Aug 9, 1988                                X3T9.2/88-93
 
    To: X3T9.2 Committee (SCSI)
 
    From: George Penokie (IBM)
 
    Subject: SCSI-2 Proposal for Non-data Errors
 
    We would like to add an indicator in the sense data
    associated with a Sense Key of Recovered Error to distinguish
    between data and non-data errors.
 
    Data errors typically are errors associated with reading or
    writing data.  Examples include the inability to recover
    information from a logical block (or the ID for a logical
    block) on a read operation, or from a record ID on a write
    operation.   Typical errors of this type are ECC or CRC
    checks in either the ID or data portion of a logical block,
    sync byte errors, or ID not found errors.
 
    Non-data errors are errors not associated with the reading or
    writing of data.  Typical errors of this type include track
    positioning errors, write circuit safety checks, spindle
    motor errors, and internally detected errors.
 
    We would like to modify section "7.1.15.1 Sense-Key Specific"
    in version 4 on page 7-69 after the IMPLEMENTORS NOTE to read
    as follows:
 
      If the sense key is RECOVERED ERROR OR MEDIUM ERROR OR
    [HARDWARE ERROR] and if the SKSV bit is one, then the
    sense-key specific field shall be defined as shown in Table
    7-xx.  These fields identify the actual number of retries
    used in attempting to recover from the error condition.
 
                Table 7-xx: Actual Retry Count Bytes
   --------------------------------------------------------------
     Bit|  7   |  6   |  5   |  4   |  3   |  2   |  1   |  0   |
   Byte |      |      |      |      |      |      |      |      |
   --------------------------------------------------------------
    15  | SKSV | D/N  |      Reserved                           |
   -----|-------------------------------------------------------|
    16  | (MSB)                                                 |
   -----|---                 Actual Retry Count              ---|
    17  |                                                 (LSB) |
   --------------------------------------------------------------
 
      [A data error/non-data error (D/N) bit of zero specifies
    that the actual retry count is a count of the number of
    attempts to recover the data.  A D/N bit of one specifies
    that the actual retry count is a count of the number of
    attempts to recover from the non-data error condition.]
 
     [IMPLEMENTORS NOTE:  Data errors are errors which occur
      during the reading or writing of data to or from a device's
      media.  Any other failure is considered a non-data error
      (i.e positioning errors, spindle speed errors, etc.).]
 
      The actual retry count field returns implementation-
    specific information on the actual number of retries used in
    attempting to recover an error or exception condition.  It is
    recommended that this field relate to the retry count fields
    specified within the error recovery parameters page of the
    MODE SELECT command.