The DRDAEXEC thread and queries from clients
For every DRDA client, IBM® Informix® creates a session and a DRDAEXEC thread, which is the equivalent of an SQLEXEC thread, to process and run the queries. This thread also formats the results of the queries in the DRDA protocol format and sends the results back to the client computer.
Queries issued from a DRDA client run in parallel if PDQPRIORITY is set and the query can run in parallel. Queries run from DRDAEXEC threads can also run in parallel.