Subject Re: [firebird-support] object is in use
Author Carlos H. Cantu
LSSBcfs> While this would avoid the error, you will not know when/if your change will be applied.
LSSBcfs> A connection can hold an object in use for an indeterminant period of time.

Dmitry said to me sometime ago that procedures changes will be
executed immediately and not get held. I tested and seems to be true
(ie: "wait" behavior is different for such case).

For the other cases, there is possibility to determine a timeout value
in the ddl transaction.

Firebird Performance in Detail - -