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 SQL SecuritySupplementary Information 

Clauses of ALTER EXTERNAL CONNECTIONS POOL

CLEAR ALL

Closes all idle connections and disassociates currently active connections;they are immediately closed when unused.

CLEAR OLDEST

Closes expired connections

SET LIFETIME

Configures the maximum lifetime of an idle connection in the pool.The default value (in seconds) is set using the parameter ExtConnPoolLifetime in firebird.conf.

SET SIZE

Configures the maximum number of idle connections in the pool.The default value is set using the parameter ExtConnPoolSize in firebird.conf.

How the Connection Pool Works

Every successful connection is associated with a pool, which maintains two lists — one for idle connections and one for active connections.When a connection in the “active” list has no active requests and no active transactions, it is assumed to be “unused”.A reset of the unused connection is attempted using an [fblangref50-management-session-reset-alter] statement and,

  • if the reset succeeds (no errors occur) the connection is moved into the “idle” list;

  • if the reset fails, the connection is closed;

  • if the pool has reached its maximum size, the oldest idle connection is closed.

  • When the lifetime of an idle connection expires, it is deleted from the pool and closed.