Dimitry Sibiryakov,
rashid.abzalov утверждает, что прям параллельно из тредов в одном коннекте все работает. Я может не те ключевые слова использую, но ... а, вот, нашел, по 10g
https://docs.oracle.com/cd/B19306_01/appdev.102/b14250/oci09adv.htm
Once spawned, threads run asynchronously with respect to one another. They can access common data elements and make OCI calls in any order. Because of this shared access to data elements, a synchronized mechanism is required to maintain the integrity of data being accessed .
The mechanism to manage data access takes the form of mutexes (mutual exclusivity locks), that is implemented to ensure that no conflicts arise between multiple threads accessing shared internal data that are opaque to users. In OCI, mutexes are granted for each environment handle.
Собственно, не вижу никакой параллельности.
Кстати, в доке на 12g уже по другому написано
http://docs.oracle.com/database/121/LNOCI/oci08sca.htm#LNOCI16587
но тем не менее
Implementing Thread Safety
Pass a value of OCI_ENV_NO_MUTEX for the mode of OCIEnvNlsCreate(). The application must set mutual exclusion locks (mutex) for OCI calls made on the same environment handle. This has the advantage that the mutex scheme can be optimized to the application design. The programmer must also ensure that only one OCI call is in process on the environment handle connection at any given time.
Pass a value of OCI_DEFAULT for the mode of OCIEnvNlsCreate(). The OCI library automatically gets a mutex on every OCI call on the same environment handle.
т.е. один хрен - по умолчанию синхронизация через мютексы, или человек сам должен эту синхронизацию делать.
