Execute Channel Program: Difference between revisions

Revision as of 16:34, 3 January 2021

Revision as of 12:28, 14 January 2021

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{{short description|Operating System low level I/O API}}

{{See also|EXCPVR}}

{{short description|Operating System low level I/O API}}

{{refimprovemore citations needed|date=June 2012}}

In [[IBM mainframe]] [[operating system]]s, '''Execute Channel Program''' ('''EXCP''') is a [[Supervisor Call instruction|supervisor call]] for low-level device access, where the programmer is responsible for providing a ''[[Channel program#Channel Program|channel program]]''—a list of device-specific commands (CCWs)—to be executed by I/O channels, control units and devices.<ref name="Hannula1974">{{cite book

| author=Reino Hannula

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| date = August 2020

| section = Chapter 4. Executing Your Own Channel Programs

| pages = 151-210151–210

| section-url = https://www-01.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf#page=181

| url = https://www-01.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf

| id = SC23-6861-40}}

</ref> is more specifically described in the OS System Programmer's Guide.;<ref>{{cite manual|publisher=IBM|title=IBM System/360 Operating System System Programmer's Guide|id=C28-6550-2|date=March 1967|url=http://www.bitsavers.org/pdf/ibm/360/os/R01-08/C28-6550-2_OSsysPrmg_Mar67.pdf}}</ref>; EXCP for [[DOS/360 and successors]]<ref name="Stotts1990">{{cite book

| author=Gary A. Stotts

| title=DOS/VSE: Introduction to the Operating System

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</ref>

This article mostly reflects OS/360 through [z/OS]; some details are different for TOS/360 and DOS/360 through [[z/VSE]].

==Specifying datasets==

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==Channel programs==

System/360 channel programs are a sequence of commands which are executed by the channel and the I/O device. Channel programs can be located anywhere in main storage. The channel program is a sequence of ''Channel Command Words'' (CCWs), which may be executed sequentially unless a branch, called ''Transfer In Channel'' (TIC), is executed, or the channel returns a [[IBM_SystemIBM System/360 architecture#CSW Status modifier|status modifier]]. Each CCW is a doubleword (eight bytes) as follows:<ref>{{cite book |last1=IBM Corporation |title=IBM System/360 Principles of Operation |date=January 1967 |pages=84-12184–121 |url=http://bitsavers.org/pdf/ibm/360/princOps/A22-6821-6_360PrincOpsJan67.pdf |access-date=Dec 4, 2019}}</ref>

<pre>

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