Maintaining The Databases; Understanding Database States; Synchronized Databases Before Starting Rdf - HP NonStop RDF J-series RVUs Management Manual

6 Maintaining the Databases

A vital task in working with RDF is to keep the backup and primary databases synchronized
with each other. This chapter, which is intended for database administrators, includes these key
topics:
• "Understanding Database States" (page 157)
• "Making Changes to Database Structures" (page 159)
• "Resynchronizing Databases" (page 164)

Understanding Database States

It is important to understand the terms used to describe the different states of a primary database
and its associated backup database. The following illustrations show synchronized and
unsynchronized databases.
In the illustrations, \PRIMARY indicates the primary system and database, and \BACKUP
indicates the backup system and database. Tx indicates the data associated with a committed
transaction. In some illustrations, the extractor and updater process operations also appear.
Figure 6-1 shows synchronized databases where RDF has just been initialized and the application
on \PRIMARY is going to be started. The databases are synchronized because they contain the
same logical data and no audit has been generated.
Figure 6-1 Synchronized Databases Before Starting RDF
Figure 6-2 shows synchronized databases where the application is running on \PRIMARY, three
more transactions (T4, T5, T6) have occurred, and RDF is in the process of applying the data
records for these transactions to the backup system. Transaction data for T4 has been applied to
the backup database. The data for T5 is still being applied to the backup database, and the data
for T6 has not yet been sent to the backup system.
Although transactions T5 and T6 have not yet been applied to the backup database, the primary
and backup databases are synchronized in that the only thing delaying the two databases from
being logically identical is the fraction of a second it takes the extractor and updaters to catch up
with the MAT.
Understanding Database States 157