The QALoad NT player can execute either process-based or thread-based virtual users, depending on the middleware used (discussed below).
A process-based virtual user will load into memory as a .EXE and use approximately 1Mb of RAM, depending on middleware and script size. Each process-based virtual user will also load up a separate middleware client resulting in higher memory overheads.
Thread-based virtual users are loaded into memory as a thread of the Player and use between 100-250K of memory, depending on middleware and script size. Only one copy of the middleware client is loaded into memory and shared by all the threaded virtual users, drastically reducing the memory overheads and processor requirements for thread-based virtual users.
I think you can use Thread safe for IIOP as it is similar to Winsock.