Oracle
Streams – High-speed replication from the Oracle log_buffer
allows fast synchronization between servers. Oracle
Streams requires Oracle10g Enterprise Edition.
Let’s take a closer look
at the cheapest solution, Oracle manual standby database.
Manual standby database
If you want to save money
by using Oracle Standard Edition which does not have Oracle
DataGuard, multimaster replication and Oracle Streams, a manual
approach might work for you. In this approach you write a
daemon process on the OS that detects when the Oracle ARCH
process has completed writing an archived redo log. Then,
the daemon uses FTP or rsh to move the archived
redo to the standby database server where it is automatically
accepted into the standby database because it remains in
“recover database” mode.
The trick to this approach
is to set the size of the online redo logs to minimize data
loss. This is done by examining the log switch rate for
the Oracle database at its PEAK DML load. For example, if
you determine a size that has log switching every 5 minutes at
peak load (with an average of, say 15 minutes, the maximum data
loss is 15 minutes.
Many shops improve this
mechanism with solid-state disk for the online redo logs and
archived redo log filesystem, SSD can write up to 100 times
faster, reducing recovery time by two orders of magnitude,
reducing the maximum data loss from 15 minutes to less than one
minute. You can see details about RAM-disk for Oracle at
this link:
http://www.storagesearch.com/texasmem-art1.html
