VERIFY 13h
Commands
177
VERIFY 13h
VERIFY verifies one or more blocks beginning with the next block on the tape. The verification is
media verification only. It reads data from the tape as it would for a read but then immediately
discards it. No data is transferred between the host and drive.
The command is identical to the
READ command in most respects. The pre-execution checks are
identical. Sense data reporting on errors/exceptions is identical. The only differences are:
• No data phases occur during verification.
• The
Verify command has no SILI bit. When an illegal length record is encountered, Verify
behaves like
READ with the SILI bit clear.
NOTE: Verify will not complete until all data has been read. It does support the ANSI “byte
compare” or “Immed” options (see the ANSI SCSI specification).
Pre-execution checks:
Command descriptor block:
CDB fields:
Illegal Field Fixed Bit Reservation Deferred Error
Unit Attention Media Access Diagnostic Status
7 6 5 4 3 2 1 0
0 Operation Code (13h)
1 Reserved (0) Immed(0) BCmp(0) Fixed
2 (MSB)
Verification Length
3
4 (LSB)
5 Control
Immed 0 The Immediate Reporting option is not supported, so this bit must be 0.
BCmp 0 The Byte compare option is not supported, so this bit must be 0.
Fixed 0 The Verification Length field specifies the length of the data to be verified in bytes.
1 The Verification field specifies the length of the data to be verified in blocks. The size
of each block (in bytes) is specified by the current block length specified in the Mode
Parameter block descriptor.
Verification
Length
0 No data is verified. This is not considered an error and the current logical position
will be unchanged.
>0 The amount of data to be verified, in bytes or blocks as specified by the Fixed field.
