When SI is trying to send a 30 MB file to SAP using SAP Suite Adapter for JCo 3.x it takes more than 3 to 5 minutes and in some cases it takes even longer.
As per IBM L3 Support team,
The current functionality of IDOC_INBOUND_ASYNCHRONOUS which is hard
coded on the SapSuiteAdapter3 ALE,
1. create TID,
2. SAP Adapter (SI) initiates the call to JCo libraries to transfer the
iDocs to SAP, JCo libraries in-turn makes calls to some Native libraries (Probably C) which in-turn, interacts with SAP system and this entire process waits for processing to occur on the idoc in SAP,
before a response is returned from SAP to SI notifying that SAP got the file and to close the ALE session. This processing has been know to keep connections and threads busy for awhile longer than possibly a different RFC outside of SI. One suggestion that has been made is to not mandate the IDOC_INBOUND_ASYNCHRONOUS and allow it to be configurable. Unfortunately, L3 has determined that this is new functionality that has never existed in the GIS/SI product code base.
To implement this functionality, it would have to be requested as an enhancement.