The LU 6.2 architecture does not permit an unlimited number of sessions between parallel-session-capable LUs. Limits are imposed on the number of sessions an LU can have for a given mode name. Limits also are imposed on the number of contention-winner sessions an LU can have for a given mode name. These limits are called session limits. Before a session can be activated between two LUs on a given mode, the session limits on that mode must be negotiated between the two LUs.

Because each mode name has its own session limits, LUs have multiple session limits. An application program might be limited, for example, to five sessions with another LU using a mode name of EXAMPLE and be able to have 10 sessions with the same LU using a mode name of TESTCASE. Session limits can be defined dynamically while the application programs are executing. LU 6.2 architecture defines control operator verbs that can be used to change session limits.