# CICS Methods of Invocation

Multiple methods of invocation are available to access and work with CICS applications and resources: containers, communication areas, transient data, storage queues, and most other entities available in CICS.

The CICS Interface enables data to be communicated to the CICS region in various methods of invocation, as follows:

1. Invokes a CICS program from the CICS interface through a DPL application.
2. Writes the formatted data buffer to a CICS TDQ for subsequent processing.
3. Writes the formatted data buffer to a CICS TSQ for subsequent processing.
4. Initiates a CICS transaction from the CICS resident Substation ES server.
5. Optionally passes the communications area (COMMAREA) or a container to initiated transactions.
6. Transfers control (XCTL) to a user application from the CICS resident Substation ES server.

The following figure shows the message flow of CICS Interface:

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