(1) In SNA, two or more concurrently active sessions between the same two logical units. Each session can have different session parameters.
(2) Two or more concurrently active sessions between the same two network addressable units using different pairs of network addresses or local-form session identifiers. Each session can have independent session parameters.
(3) A single intersystem link that can carry multiple independent sessions. Parallel sessions are supported by CICS intersystem communication (ISC).