Table of Contents
Advertisement
Command Processing
2.8.4 Error recovery processing
When an error which it is possible to retry is detected in the IDD, the IDD
attempts error recovery processing of the detected error during command
execution.
The INIT can specify whether or not to report detailed parameters and
successfully recovered errors related to error recovery processing using either the
MODE SELECT or the MODE SELECT EXTENDED command. Also, by the
INIT specifying those parameters, they can be saved in the system space on the
disk medium and they can be changed temporarily without being saved. After the
power is turned on, or after reset, the IDD reads out the saved parameters and
initializes the error recovery processing procedure.
See Chapter 4, "Command Specifications" concerning details of the MODE
SELECT and MODE SELECT EXTENDED commands.
An outline of the error recovery processing executed by the IDD is shown below.
(1) Recovery procedures for disk drive errors
The IDD executes error recovery processing like that shown in Table 2.8 for errors
detected during data access on the disk medium. Caution is necessary when
performing these recovery processing procedures, because they are accompanied
by rotational delays for repositioning data blocks on the disk medium or by added
command processing time due to initialization of the positioning control system,
etc.
The INIT can control the number of retries by page 1 (Read/Write error recovery
parameters), page 7 (Verify error recovery parameters) or page 21 (Additional
error recovery parameters) of the MODE SELECT parameters, but during normal
use, it is recommended that the default values specified by the IDD be used.
Table 2.8 Outline of disk drive error recovery processing
Item
Type of Error
1
Seek Error
2
Uncorrectable Data Error
3
Correctable Data Error
2-16
Error Recovery Processing
Rezero (Return to Zero Cylinder), readjustment of
positioning control system, and repositioning to the data
block.
Reread
Correct by ECC.
C141-C009
Advertisement
Table of Contents
