Synchronized database

Hello Everyone !

Our application has to support over a hundred terminals, and we want to distribute the workload on two AIX-boxes. The idea is that every system serves a part of the database, and the two systems are connected via SQL*NET.

So far, so well... but in case of one computer going down, we want to be able to do out application on _one_ system (with degraded performance, but better than a complete blackout :-).

The basic idea is that SystemA (with instance PRDA) must have a copy of the database of SystemB (with instance PRDB). SystemB must send its archive-logs to SystemA, where they are stored. If SystemB is unavailable, we start instance PRDB on SystemA and are rolling the database with the archive-logs, so we get a "current" copy of PRDB.

This will look something like this:

+---------------+                        +---------------+                       


+ System A      +                        + System B      +


+---------------+                        +---------------+


+  PRDA (up)    + <--SQL*Net-+           + PRDA (down)   +


+---------------+            I           +---------------+


+ Archive-Log A + ---------------------> + Archive-Log A +


+---------------+            I           +---------------+


+  PRD B (down) +            +---------> + PRDB (up)     +


+---------------+                        +---------------+


+ Archive-Log B + <--------------------  + Archive-Log B +


----------------+                        +---------------+

Sending of the logs between the systems looks simple: just copy them between the two systems (via NFS or maybe RCP).

But what do we do with the _online_ redo logs ? I think it is not very wise to copy them over the network every second or something like that....

How can I "synchronize" the two systems ? Are there products available which can do such a task ? Is SQL*NET capable of doing such things (havent purchased it yet) ? Any other ideas or different apporaches to this problem ?

Any ideas are welcome.

Willy Klotz

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