RDF System Management Manual for J-series and H-series RVUs (RDF 1.10)

7 Online Database Synchronization
With RDF/IMP, IMPX, or ZLT you can synchronize entire databases or selected volumes, files,
tables or even partitions while your applications continue to run.
For information about NonStop SQL/MX databases, see Chapter 16 (page 307).
Overview
The RDF online database synchronization protocol consists of the following general steps (the
details of which are discussed later in this chapter):
• Initialize the RDF configuration with the SYNCHDBTIME option.
• Issue a START RDF, UPDATE OFF command.
• Get a copy of the database by one of two methods:
Method 1–
– This method does not work for entry-sequenced files or tables, nor does it work for
NonStop SQL tables that have SYSKEYs or clustering keys.
– Create an empty copy of the database.
– Load the data from the actual database into the copy with shared access. Because
the load operation with shared access reads through locks held by applications, the
resulting files are inconsistent with respect to transactions, but it is consistent with
respect to the physical state.
– Method 2
– This method works for entry-sequenced files or tables, as well as for NonStop SQL
tables that have SYSKEYs or clustering keys.
– Take an online dump of your database
– Perform a File Recovery to a New Location (FRNL) from the online dump you have
just taken above.
• Load the data from the actual database into the copy with shared access. Because the load
operation with shared access reads through transaction locks held by applications, the resulting
file is inconsistent with respect to transactions, but it is consistent with respect to its physical
state.
• When you have completed getting a copy of your database by either of the methods stated
above and you have moved the copy to the backup system, issue a START UPDATE command.
As the updaters start applying audit, they put the backup database to a consistent state with
regard to transactions.
The RDF online database synchronization protocol can be used to synchronize entire databases
or selected parts of databases. The operations can be complex, depending upon the database
system being used (NonStop SQL/MP, NonStop SQL/MX, or Enscribe), the file types being used
(key-sequenced and relative), and whether you need to synchronize an entire database or just
selected portions. If you need to synchronize entire databases, you should first read “Synchronizing
Entire Databases Online” and “Considerations When Synchronizing Entire Databases” (page 160).
Because you must run RDF with UPDATE OFF while you obtain a copy of the database, audit data
will collect in the RDF image trails before you can eventually start the updaters. Therefore, if your
database is very large, you might want to consider synchronizing several volumes at a time
(synchronize a subset of volumes and then start updating. When the updaters are caught up, stop
RDF and reinitialize RDF using synchdbtime. Then do the same with the next subset of volumes).
158 Online Database Synchronization