User table
The user table tracks all user threads and system threads.
Each client session has one primary thread and zero-to-many secondary threads, depending on the level of parallelism specified. System threads include one to monitor and control checkpoints, one to process onmode commands, the B-tree scanner threads, and page-cleaner threads.
The database server increases the number of entries in the user table as necessary. You can monitor user threads with the onstat -u command.