While using the DB Access Module for Oracle OCI, the database callbacks are invoked with respect to the allocation and deallocation of OCI Environment Handle OCIEnv. The connection callbacks are invoked with respect to the allocation, deallocation, connect and disconnect of the OCI Service Context Handle OCISvcCtx. Please refer to the DB Interface Module User's Guide for more information.

The XA Access Module for Oracle OCI does not allocate and deallocate OCIEnv and OCISvcCtx handles; it just fetches them. Hence, the database callbacks are invoked before and after fetching the OCIEnv. Callbacks preConnAllocate, postConnAllocate, and preConnect are called before fetching the OCISvcCtx. Callback postConnect is called after fetching the OCISvcCtx.