You can specify logical block protection for read and write
operations, or only for write operations. You can also disable logical
block protection if it is enabled. By default, logical block protection
is disabled because of performance effects that result from CRC validation
on the server and the tape drive.
About this task
Read/write operations to empty or filling volumes depend
on whether the volumes have logical block protection. Protected and
unprotected data blocks cannot be mixed on the same volume. If you
change the setting for logical block protection, the change applies
only to empty volumes. Filling and full volumes maintain their status
of logical block protection until they are empty and ready to be refilled.
For example, suppose that you disable logical block protection. If
the server selects a volume that is associated with a device class
that has logical block protection, the server continues writing protected
data to the volume.
To enable logical block protection, specify
the LBPROTECT parameter on the DEFINE
DEVCLASS or the UPDATE DEVCLASS command
for the 3592, LTO, and ECARTRIDGE
device types:
Procedure
- To enable logical block protection, specify a value of READWRITE or WRITEONLY for
the LBPROTECT parameter.
For
example, to specify logical block protection during read/write operations
for a 3592 device class that is named 3592_lbprotect, issue the following
command:
define devclass 3592_lbprotect library=3594 lbprotect=readwrite
Tips: - If you update the value of the LBPROTECT parameter
from NO to READWRITE or WRITEONLY and
the server selects a filling volume without logical block protection
for write operations, the server issues a message each time the volume
is mounted. The message indicates that data is written to the volume
without logical block protection. To prevent this message from displaying
or to have Tivoli® Storage
Manager write
data only with logical block protection, update the access of filling
volumes without logical block protection to read-only.
- To reduce the performance effects, do not specify the CRCDATA parameter
on the DEFINE STGPOOL or UPDATE STGPOOL command.
- When data is validated during read operations by both the drive
and by the Tivoli Storage
Manager server,
it can slow server performance during restore and retrieval operations.
If the time that is required for restore and retrieval operations
is critical, you can change the setting of the LBPROTECT parameter
from READWRITE to WRITEONLY to increase
the restore or retrieval speed. After data is restored or retrieved,
you can reset the LBPROTECT parameter to READWRITE.
- To disable logical block protection, specify a value of NO for
the LBPROTECT parameter.
Restriction: If logical block protection is disabled, the server
does not write to an empty tape with logical block protection. However,
if a filling volume with logical block protection is selected, the
server continues to write to the volume with logical block protection.
To prevent the server from writing to tapes with logical block protection,
change access of filling volumes with logical block protection to
read-only. When data is read, the CRC on each block is not checked
by either drive or the server.
If a disaster occurs and the disaster
recovery site does not have drives that support logical block protection,
you must set the LBPROTECT parameter to NO.
If the tape drives are used for write operations, you must change
the volume access for volumes with protected data to read-only to
prevent the server from using the volumes.
If the server is
to enable logical block protection, the server issues an error message
that indicates that the drive does not support logical block protection.
What to do next
To determine whether a volume has logical block protection, issue
the QUERY VOLUME command and verify the value in
the field Logical Block Protection.