RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Online Database Synchronization
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
7-14
Partial Database Synchronization Considerations
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.
Key-Sequenced Tables
The most effective means of describing this method is to use an example. Suppose you
have a table named PART whose primary partition is named $DATA.TEST.PART, that
this table has 50 secondary partitions, and you only need to synchronize the primary
partition. The following set of steps presumes you have just added the volume needing
synchronization to the RDF configuration and you are running with update off.
Note. Because the SQLCI LOAD operation generates new SYSKEY values in the backup
table, key-sequenced tables containing SYSKEYs cannot be synchronized online.