Pause, Release, and Transfer are callable services that enable you to synchronize task processing with minimal overhead. If you have, for example, an application that requires two or more tasks to trade control back and forth, these services provide efficient transfers of control.
These services, which are available to both unauthorized and authorized callers in Assembler as well as C or C++, use a system-managed object called a pause element to synchronize processing of tasks. The services provide the following functions:
| Callable service | 64-bit version callable service | Description |
|---|---|---|
| IEAVAPE, IEAVAPE2 | IEA4APE, IEA4APE2 | Obtains a pause element token (PET), which uniquely identifies a pause element (PE). |
| IEAVDPE, IEAVDPE2 | IEA4DPE, IEA4DPE2 | Frees a pause element (PE) that is no longer needed. |
| IEAVPSE, IEAVPSE2 | IEA4PSE, IEA4PSE2 | Pauses the current task or SRB. |
| IEAVRLS, IEAVRLS2 | IEA4RLS, IEA4RLS2 | Releases a paused task or SRB. |
| IEAVRPI, IEAVRPI2 | IEA4RPI, IEA4RPI2 | Retrieves information about a pause element (PE). |
| IEAVTPE | IEA4TPE | Tests a pause element (PE) and determines its state. |
| IEAVXFR, IEAVXFR2 | IEA4XFR, IEA4XFR2 | Releases a paused task and, when possible, gives it immediate control, while optionally pausing the task under which the Transfer request is made. |
The services use a system-managed pause element (PE) rather than an application-managed control block, such as an event control block (ECB), thus reducing the possibility of error that might come from improper reuse of the control block.
As a PE is much like an ECB, the Pause service is much like the WAIT macro, and the Release service is much like the POST macro. Just as you can use POST to keep a task from waiting by preposting, you can use Release to keep a task from pausing by prereleasing.
The Transfer service can both release a paused task and pass control directly to the released task. The Transfer service can also pause the task that calls the service. Thus, Transfer enables quick dispatches, saving the overhead of work search. It also allows two tasks to trade control back and forth with minimal overhead.
To understand how to use the services, you need to know more about pause elements, (PEs) and the pause element tokens (PETs) that identify them.