[bubuna]

hi all,

I'm not sure whether should i post my question here.
I'm doing a program that have 2 modes, which are live database and offline database. Live database is from server and offline database is in local database(as a back up-when server down, it still can work without interrupt). i got 3 PCs and 1 server, so if there are 2 pc's connection encounter problem and need to run offline database, then how am i going to make sure the data is consistent after the connection is okay?
for example, if i have a table with an auto increment column as the primary key, and what if the 2 of PCs need to run in offline database, and after connection is up then how can i get a consistent data(as currently after the connection is up, then the 2 offline databases restore the data back to live database then they may have duplicated data happened).
Anyone can help on this? or any suggestion?

[Icepick.pt]

Your backup servers must be replications of the main one.

Basically, you need to set up a replication configuration, in wich your two slave servers are updating every change that occurs on the master. Obviously, replication assumes that the slaves do not make any database change outside the replication schema.

The replication is conducted through both the master and the slaves logs.
This means that you can cut comunication between master and slaves at any time. When connection is available again, the slaves will catch up from the master logs from the point they have stopped.

Replication is fairly easy on MySQL but you may want to have a professional doing this, depending on how precious the consistency of your data is.