The SQL passthrough can be used with solidDB® High Availability.
Basic connectivity
In normal operation, all the passthrough processing takes place in the Primary server, unless load balancing is used.
Transparent Connectivity with load balancing
When load balancing is enacted (PREFERRED_ACCESS=READ_MOSTLY), the Secondary server is capable of performing the passthrough on read statements. All the non-read statements are directed to the Primary server by using the normal transaction hand-over mechanism.
Server failovers
SQL passthrough operates correctly in the presence of HotStanby failovers, following the normal rules:
▪All the transaction that are mid-way (active) are aborted in a failover.
▪All transactions that are committed are also successfully committed in the backend.
Using transparent failover
If transparent connectivity is used, failure transparency level must be set to TF_LEVEL=SESSION to retain the session passthrough mode over the connection failover. In the other case (TF_LEVEL=CONNECTION), the session-specific passthrough mode is lost and passthrough operates as on a new connection.
Backend failovers
SQL passthrough does not support backend failovers.