gtpg1m0g | General Information |
In a TPF system, a unit of work is generally started by a message received from the user of a terminal or workstation or another processor. When a TPF system receives a message, it assigns a storage block called an entry control block (ECB) to the message. The term entry refers to the processing associated with an ECB. An entry is the unit of work in the TPF system The life of an entry is measured from the creation to the deletion of the ECB. Programs that require an ECB are called E-type or ECB-controlled programs.
The TPF system is an interrupt-driven system. Interrupts occur as a result of the receipt of a message, the completion of a file request, and the processing of a supervisor call macro. When an entry completes processing, or when an entry requests a service that requires that entry to wait, a TPF control program finds the next entry for processing.
The TPF system uses lists to schedule and dispatch entries. Entries are processed in a priority sequence that allows those entries in progress to complete before new entries are started. The fast response time to individual entries is achieved in part by this technique.