August 2000
Intermediate to advanced
288 pages
7h 50m
English
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Failover Complexity
The complexity of the failover process depends on the status of the client applications when the primary database fails. Failover of database applications can be divided into two broad categories, based on the status of the database connection at the time of failure:
- Connect-time failover
This type of
.
- Runtime failover
This type of failover occurs when a client application has already connected to the primary database, and the database then fails. Clients may or may not have an active transaction at the time of the failure.
The following sections describe conceptually the actions that are needed in the backup database in order to re-create the same state for the clients as they had in the primary database at the time the failure occurred.
Tip
Failover does not take care of failure at all levels. If a client application terminates for any reason or if the client system crashes, database failover mechanisms do not help. Failover mechanisms are designed only to handle database failures. In the case of client failure, the client application must be restarted by some other means.
Connect-Time Failover
Connect-time failover occurs when the primary database fails either before or during the connection attempt. The only thing then required for a successful failover is for the client application to connect to the backup database instead of ...
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