RDF System Management Manual

Online Database Synchronization
HP NonStop RDF System Management Manual—524388-003
7-17
Partial Database Synchronization Issues
Described below is a set of steps that can be used to synchronize individual partitions
of NonStop SQL/MP tables (either primary or secondary partitions).
Requirements for Synchronization of Individual Partitions
The following methods work only if all the partitions of a given table still reside on disk
on the backup system. If you do not have all partitions of a given table backed up on
tape and you encounter a total media failure that destroys or renders a volume
inoperable on your backup system, then you might have to synchronize your entire
table.
To prevent this you should take the precaution of having all tables backed up in their
entirety on tape. With the protocol for synchronizing individual tables below, however,
this does not mean you have to back up all tables on your backup system with all
current data. Rather, you can use the following method, which will be very fast and will
enable fast resynchronization should you ever encounter a complete media failure that
requires resynchronization of individual partitions of a table.
1. Rename the table to a temporary name using the SQLCI ALTER TABLE
command.
2. Create a duplicate table with the original name of the table you renamed in step 1.
This table must have all the same partitions as the original table.
3. Use BACKUP to put the duplicate table on tape. It will have all the partitions, but
they are empty. Thus, it will not take long to back the partitions up, nor will it take
long to restore any of the partitions.
4. Rename the table to a temporary name and then drop it. By renaming it before
dropping it, you preserve any indexes that are associated with the original table
name.
5. Rename the temporary table (step 1) back to the original table name.
Thus, you now have on tape empty partitions for the entire table. Should you ever
lose a volume to a complete media failure, you can install a new disk and then use the
RESTORE utility with the PARTONLY option to recover the missing partition. Note
that because you have backed up a table with the name you need on the backup
system, you can restore any partition that you need to with the PARTONLY option and
without having to use the MAP NAMES option. Once you have restored the empty
partition, you can use the protocol described below to synchronize the affected
partition.
Note that there is no recovery for a media failure that wipes out an individual partition
of a partitioned index. If that happens, you will need to drop the index from the
associated table, thereby eliminating all other partitions of the index. Then you must
create a new index.