HP 3000 Manuals HP 3000 Manuals
Improving Storing Efficiency by Increasing Record Size (MAXTAPEBUF)
Files are stored with greater efficiency by using the maximum backup
record (buffer) size allocated to a given backup device. Performance
increases because data transmission is more efficient and because the
amount of media used for interrecord gaps decreases.
The maximum backup record size of MPE/iX supported backup devices differs
from device to device and is shown in Table 6-1 .
Table 6-1. Maximum Tape Record Sizes
-----------------------------------
| |
| Tape Drive Record Size |
| |
-----------------------------------
| |
| HP 7974 16 KB |
| |
| HP 7978A 16 KB |
| |
| HP 7978B 32 KB |
| |
| HP 7979 32 KB |
| |
| HP 7980(XC,S,SX) 32 KB |
| |
| DDS (all) 32 KB |
| |
| 3480 32KB |
| |
| MO 32KB |
| |
-----------------------------------
Normally when a STORE command is issued, a default record size of 16
kilobytes is utilized. However, by using the MAXTAPEBUF parameter of the
STORE command, the maximum record size of the specified device is
automatically used. If multiple backup devices are specified, using the
STORESET parameter, in conjunction with MAXTAPEBUF, STORE uses the
maximum record size, which is the lowest common denominator of the
different devices. This is necessary to ensure that the record sizes are
the same on all volumes of the backup set.
NOTE Do not use the MAXTAPEBUF parameter with a backup device of 32 KB
record size if you anticipate that you will later restore the
backup created to a backup device whose maximum record size is 16
KB. Restoring a backup to a larger maximum record size device, on
the other hand, does not cause any problem.
To increase record size when storing files, use the MAXTAPEBUF parameter
in your STORE command. For example:
FILE T;DEV=TAPE
STORE @.OPERATOR.SYS;*T;MAXTAPEBUF