Blocksize; Guidelines - HP BACKCOPY Reference Manual

BACKUP and RESTORE can be used with the TMFCOM DUMP command for disks containing
a combination of audited and nonaudited files or for disks that contain only audited files:
1. Ensure the safe and complete recovery of files when media recovery is needed. At a SCF
prompt, type:
1> CONTROL DISK $DATA, REFRESH
2> BACKUP $TAPE, $DATA.*.*,OPEN,AUDITED, &
2> &PARTONLY ON ,LISTALL
3> TMFCOM DUMP FILES $DATA.*.*
The SCF CONTROL DISK, REFRESH command updates the file labels and writes all
changed buffers to the disk.
The backup includes nonaudited and audited files.
The online dump performed by TMFCOM DUMP includes only audited files, and ensures
that there is an accessible copy of these files if TMF fails.
If the disk (in this case $DATA) becomes damaged or unusable, recover the files on a
new disk that is properly labeled and initialized using SCF.
2. RESTORE is used to restore the nonaudited files, and TMFCOM is used to recover the
audited files. For example:
4> RESTORE $TAPE, $DATA.*.*,OPEN,PARTONLY ON,LISTALL
5> TMFCOM RECOVER FILES $DATA.*.*
The AUDITED option is omitted in the RESTORE command so that only the nonaudited
files are restored. After the RESTORE operation, the audited files are recovered using the
TMFCOM utility.
For more information on backing up open files, see

BLOCKSIZE

The BLOCKSIZE option specifies the size of each tape record (block) written to the backup tape.
BLOCKSIZE data-record-size
data-record-size
is the number of 1024-byte increments (blocks) in each record. Specify data-record-size
as 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, or 52. The actual blocks written to tape
include sequence numbers, checksums, and address information, so they are slightly larger
than 1024 * data-record-size.
NOTE:
Marathon 3216 controllers. All other transfers must be in the range of 2 KB through 28 KB.

Guidelines

BLOCKSIZE can be an even value in the range 2 through 52, but BACKUP rounds it down to
a multiple of 4 (unless BLOCKSIZE is 2). Rounding is performed because when DP2 tapes are
to be generated (tape format 2 or greater) and BLOCKSIZE is 4 or greater, BACKUP and the
DP2 disk process perform integrity checking by reading whole-structured file blocks of length
50 BACKUP
Data transfer sizes larger than 28 KB are only supported by the Napa 3215 and
OPEN (page 61).