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<title>Execute Channel Program</title>

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</style><div role="note" class="hatnote navigation-not-searchable">See also: <a href="EXCPVR" class="mw-redirect" title="EXCPVR">EXCPVR</a></div>

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<p>In <a href="IBM_mainframe" title="IBM mainframe">IBM mainframe</a> <a href="Operating_system" title="Operating system">operating systems</a>, <b>Execute Channel Program</b> (<b>EXCP</b>) is a <a href="Macro_(computer_science)" title="Macro (computer science)">macro</a> generating a <a href="System_call" title="System call">system call</a>, implemented as a <a href="Supervisor_Call_instruction" title="Supervisor Call instruction">Supervisor Call instruction</a>, for low-level device access, where the programmer is responsible for providing a <i><a href="Channel_program" class="mw-redirect" title="Channel program">channel program</a></i>—a list of device-specific commands (CCWs)—to be executed by I/O channels, control units and devices.<sup id="cite_ref-Hannula1974_1-0" class="reference"><a href="#cite_note-Hannula1974-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Kapur1970_2-0" class="reference"><a href="#cite_note-Kapur1970-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> EXCP for <a href="OS/360_and_successors" title="OS/360 and successors">OS/360 and successors</a><sup id="cite_ref-Johnson1989_3-0" class="reference"><a href="#cite_note-Johnson1989-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> is more specifically described in the OS System Programmer's Guide.;<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> EXCP for <a href="DOS/360_and_successors" title="DOS/360 and successors">DOS/360 and successors</a><sup id="cite_ref-Stotts1990_6-0" class="reference"><a href="#cite_note-Stotts1990-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> is more specifically described in DOS Supervisor and I/O Macros.<sup id="cite_ref-GC24-S037-12_7-0" class="reference"><a href="#cite_note-GC24-S037-12-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-SC34-2709_8-0" class="reference"><a href="#cite_note-SC34-2709-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>

This article mostly reflects OS/360 through <a href="Z/OS" title="Z/OS">z/OS</a>; some details are different for TOS/360 and DOS/360 through <a href="Z/VSE" class="mw-redirect" title="Z/VSE">z/VSE</a>.

</p>

<div class="mw-heading mw-heading2"><h2 id="Specifying_datasets">Specifying datasets</h2></div>

<p>Using EXCP, legacy devices and legacy datasets may be operated on with relatively high performance. EXCP devices are OPENed (that is, are made available to the application) by specifying the <a href="Data_Control_Block" title="Data Control Block">Data Control Block</a> (DCB) for OS and the DTFPH for DOS.

</p>

<div class="mw-heading mw-heading2"><h2 id="Specifying_I/O_operations">Specifying I/O operations</h2></div>

<p>For OS/360 through z/OS, the program provides an <i>Input/Output Block</i> (IOB) to EXCP; if the program executes an EXCP to multiple IOBs, the system processes them in the order that they were requested. For DASD the IOB includes a seek address, <i>IOBSEEK</i>, in the format MBBCCHHR, where M is the extent, BB is the bin for a data cell, CCHH is the cylinder and head, and R is the record number.

</p>

<div class="mw-heading mw-heading2"><h2 id="Appendages">Appendages</h2></div>

<p>"An appendage is a programmer-written routine that provides additional

control over I/O operations during channel program execution."<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> A comprehensive list of <i>appendages</i><sup id="cite_ref-FOOTNOTEDFSMSdfp199–200[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage229_EXCP_and_EXCPVR_Appendages]_10-0" class="reference"><a href="#cite_note-FOOTNOTEDFSMSdfp199–200[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage229_EXCP_and_EXCPVR_Appendages]-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> (<a href="User_exit" title="User exit">exits</a> in the EXCP context) allows authorized programs<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup> to override or augment many of the system security and data integrity checks. Most of these appendages are supported for compatibility with earlier instances of the OS, but the functions of several have been modified or extended for MVS. The appendages are specified in the DCB as the last two characters of the module name IGG019xx, where xx = WA to Z9, inclusive. These module names are reserved for installation-written appendages. Any other name of the form IGG019xx is reserved for use by IBM access methods.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>b<span class="cite-bracket">]</span></a></sup> Appendages must reside in SYS1.SVCLIB (SYS1.LPALIB in SVS or later instances of the OS).

</p>

<div class="mw-heading mw-heading2"><h2 id="Dataset_integrity">Dataset integrity</h2></div>

<p>Normally, when a program OPENs a DCB for EXCP, OPEN creates a <i>Data Extent Block</i> (DEB) containing each <i><a href="Extent_(file_systems)" title="Extent (file systems)">extent</a></i> for the first volume of the associated dataset; however, for <i>parallel mount</i> OPEN creates a DEB containing all extents for all volumes. Each DEB is forward- and backward-chained to the DCB, and EXCP checks the chaining as a system security measure, as the DCB resides in unprotected user storage whereas the DEB resides in protected system storage, Subpool 253; in OS/VS1 and OS/VS2 EXCP uses DEBCHK to ensure that the DEB was created by OPEN. For DASD, EXCP checks that the seek address in the IOB is within one of the extents, and uses a <i>Set File Mask</i> to, e.g. indicate whether the extent is cylinder or track oriented, whether write is permitted; this prevents a seek out of the specified track (cylinder). If the programmer tries to read past the end of the track (cylinder), a <i>unit check</i> occurs and error recovery restarts the channel program with the next track (cylinder) of the current extent. If the operation goes beyond the end of the extent, EXCP calls the <i>end of extent</i> appendage, which may update the IOB and request either that EXCP reissue the request or that EXCP terminate it.

</p>

<div class="mw-heading mw-heading2"><h2 id="Legacy_datasets_only">Legacy datasets only</h2></div>

<p>EXCP is sometimes confused with a direct access storage device access method, but it is not for direct access storage devices exclusively; rather, it is a general purpose low-level device access interface which supports any <i>legacy</i> device type and any <i>legacy</i> dataset organization. For accessing <i>all</i> device types and <i>all</i> dataset organizations, the more general privileged <a href="Start_Input/Output" title="Start Input/Output">Start Input/Output</a> interface (STARTIO) is available in MVS/370 and subsequent instances of the OS although it is not an officially supported interface.

</p>

<div class="mw-heading mw-heading2"><h2 id="Simplified_operations_on_direct_access_datasets">Simplified operations on direct access datasets</h2></div>

<p>A variation of EXCP is <a href="Execute_Direct_Access_Program" title="Execute Direct Access Program">Execute Direct Access Program</a> (XDAP), which is used for accessing direct access storage only, and is provided for reading and updating existing direct access storage records. XDAP cannot be used to add records, but XDAP can be utilized along with BSAM or BPAM to effect record additions to such datasets, and several OS components utilize XDAP in this manner (the Linkage Editor, IEWL, in particular).

</p>

<div class="mw-heading mw-heading2"><h2 id="Telecommunications_device_access">Telecommunications device access</h2></div>

<p>EXCP may also be used to access communications devices attached to <a href="IBM_2701" class="mw-redirect" title="IBM 2701">IBM 2701</a>, <a href="270x" class="mw-redirect" title="270x">2702</a> and <a href="270x" class="mw-redirect" title="270x">2703</a> communications controllers and IBM 370x or Amdahl 470x front-end processors (and their respective follow-ons) operating in emulator mode (EP) or partitioned emulator mode (PEP).

</p>

<div class="mw-heading mw-heading2"><h2 id="Relationship_to_supervisor">Relationship to supervisor</h2></div>

<p>EXCP's front-end is always in <a href="Task_Control_Block" title="Task Control Block">Task Control Block</a> (TCB) mode, The normal mode for applications,<sup id="cite_ref-SoftwareAG_14-0" class="reference"><a href="#cite_note-SoftwareAG-14"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> as EXCP is a Type 1 <a href="Supervisor_Call_instruction" title="Supervisor Call instruction">SVC</a>.

</p><p>In MVS/370 and subsequent instances of the OS, the EXCP processor invokes <a href="Start_Input/Output" title="Start Input/Output">STARTIO</a> to schedule execution of the channel program. Although the EXCP processor's back-end is always in <a href="Service_Request_Block" title="Service Request Block">Service Request Block</a><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (SRB) mode,<sup id="cite_ref-SoftwareAG_14-1" class="reference"><a href="#cite_note-SoftwareAG-14"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> the back-end contains emulation code which allows the appendages developed for earlier, pre-MVS instances of the OS, specifically for EXCP, to function largely as before and thereby to appear to be in TCB mode, for which these appendages were originally designed. This distinction can complicate conversion of certain roll-your-own access methods and applications to MVS.

</p>

<div class="mw-heading mw-heading2"><h2 id="Channel_programs">Channel programs</h2></div>

<p>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 <i>Channel Command Words</i> (CCWs), which may be executed sequentially unless a branch, called <i>Transfer In Channel</i> (TIC), is executed, or the channel returns a <a href="IBM_System/360_architecture#CSW_Status_modifier" title="IBM System/360 architecture">status modifier</a>. Each CCW is a doubleword (eight bytes) as follows:<sup id="cite_ref-FOOTNOTES36084–121[httpbitsaversorgpdfibm360princOpsA22-6821-6_360PrincOpsJan67pdfpage87_Input/Output_Operations]_16-0" class="reference"><a href="#cite_note-FOOTNOTES36084–121[httpbitsaversorgpdfibm360princOpsA22-6821-6_360PrincOpsJan67pdfpage87_Input/Output_Operations]-16"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>d<span class="cite-bracket">]</span></a></sup>

</p>

<pre> bit 0 7 8 31

+--------+-----------------------+

|Command | Data address |

+--------+-----------------------+

32 36 40 47 48 63

+------+---+--------+------------+

+------+---+--------+------------+

</pre>

<p>Six commands are defined, in the low-order bits of the command field (0-7). The high-order four (or six) bits are <i>modifiers</i> ('M') for some commands, or are ignored. The commands are:

</p>

<pre> 0100 - Sense

1000 - Transfer in Channel (TIC)

1100 - Read backward

--01 - Write

--10 - Read

--11 - Control

</pre>

<p>The data address (8-31) is the 24-bit address of a main storage buffer area to or from which the data is to be transferred.

</p><p>The flag bits (32-36) are defined as follows:

</p>

<th>Description

</th></tr>

<tr>

<td>Chain data</td>

<td>Use the storage area specified in the next CCW to continue this command

</td></tr>

<tr>

<td>Chain command</td>

<td>Execute the next sequential CCW when this command completes<br> if CC or CD are not set, the channel program terminates after executing this command

</td></tr>

<tr>

<td>Suppress length indication</td>

<td>Ignore incorrect length for this command

</td></tr>

<tr>

<td>Suppress data transfer for this command

</td></tr>

<tr>

<td>Program controlled interruption</td>

<td>Generate an interrupt when this command starts executing

</td></tr></tbody></table>

<p>The count field (48-63) indicate the number of bytes to be transferred by this command.

</p><p>All eight bits of commands that initiate I/O operations are passed to the device. "The modifier bits specify to the device how the command is to be executed." For example, for the <a href="IBM_2305" class="mw-redirect" title="IBM 2305">IBM 2305</a> DASD the <i>write</i> command ('MMMMMM01'BX) may have the following values:<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup>

</p>

<th>Bit value</th>

<th>Hexadecimal</th>

<th>Description

</th></tr>

<tr>

<td>Write home address

</td></tr>

<tr>

<td>Write record 0

</td></tr>

<tr>

<td>Erase

</td></tr>

<tr>

<td>Write count, key, and data

</td></tr>

<tr>

<td>Write special count, key, and data

</td></tr>

<tr>

<td>Write data

</td></tr>

<tr>

<td>Write key and data

</td></tr></tbody></table>

<div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2></div>

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<li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text">There are several type of authorization for the use of appendages:

<ul><li>A program that is APF authorized, running in a system (0-7) key or in Supervisor Mode may use any appendage.</li>

<li>A program may use any appendage that is automatically selected by OPEN for the use of an access method.</li>

<li>A program may use any appendage that is defined at IPL time in IEAAPP00.<sup id="cite_ref-FOOTNOTEDFSMSdfp201–202[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage231_The_Authorized_Appendage_List_(IEAAPP00)]_11-0" class="reference"><a href="#cite_note-FOOTNOTEDFSMSdfp201–202[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage231_The_Authorized_Appendage_List_(IEAAPP00)]-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup></li></ul>

</span></li>

<li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text">IGG = I/O Support component prefix; 019 = Open SVC sub-component; xx = sub-function</span>

</li>

<li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">In OS/360, OS/VS1 and SVS there is no SRB mode and appendages run with interrupts disabled.</span>

</li>

<li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text">Successorss add additional flags and formats

<dl><dt><a href="IBM_System/370" title="IBM System/370">System/370</a> with Dynamic Address Translation</dt>

<dd>Adds the Channel Indirect Data Addressingfeature<sup id="cite_ref-FOOTNOTES37013-45–13-46[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage396_CHANNEL_INDIRECT_DATA_ADDRESSING]_17-0" class="reference"><a href="#cite_note-FOOTNOTES37013-45–13-46[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage396_CHANNEL_INDIRECT_DATA_ADDRESSING]-17"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> and the Indirect Data Address<sup id="cite_ref-FOOTNOTES37013-38[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage389_CHANNEL-COMMAND_WORD]_18-0" class="reference"><a href="#cite_note-FOOTNOTES37013-38[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage389_CHANNEL-COMMAND_WORD]-18"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> CCW flag.</dd>

<dt><a href="IBM_System/370-XA" title="IBM System/370-XA">System/370-XA</a></dt>

<dd>Adds format 1 CCWs<sup id="cite_ref-FOOTNOTES370-XA[httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage385_15-24-15-25][httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage384_Channel-Command_Word]_19-0" class="reference"><a href="#cite_note-FOOTNOTES370-XA[httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage385_15-24-15-25][httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage384_Channel-Command_Word]-19"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> with 31-bit addresses</dd></dl>

</span></li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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<dd><cite id="CITEREFzArch" class="citation book cs1"><a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/360/princOps/A22-6821-6_360PrincOpsJan67.pdf"><i>z/Architecture - Principles of Operation</i></a> <span class="cs1-format">(PDF)</span> (Fourteenth ed.). <a href="IBM" title="IBM">IBM</a>. May 2022. SA22-7832-13<span class="reference-accessdate">. Retrieved <span class="nowrap">Dec 4,</span> 2019</span>.</cite></dd>

<dt>DFSMSdfp</dt>

<dd><cite id="CITEREFDFSMSdfp" class="citation book cs1"><a rel="nofollow" class="external text" href="https://www.ibm.com/servers/resourcelink/svc00100.nsf"><i>z/OS Version 2 Release 4 DFSMSdfp Advanced Services</i></a>. <a href="IBM" title="IBM">IBM</a>. August 2020. SC23-6861-40.</cite></dd></dl>

<li id="cite_note-Hannula1974-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Hannula1974_1-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFReino_Hannula1974" class="citation book cs1">Reino Hannula (1974). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=0MgmAAAAMAAJ"><i>Computers and Programming: A System/360-370 Assembler Language Approach</i></a>. Houghton Mifflin. p. 431. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-395-16796-0</bdi>.</cite></span>

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<li id="cite_note-Kapur1970-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-Kapur1970_2-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFGopal_K._Kapur1970" class="citation book cs1">Gopal K. Kapur (1 January 1970). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/ibm360assemblerl00kapu/page/453"><i>IBM 360 Assembler Language Programming</i></a></span>. John Wiley & Sons. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/ibm360assemblerl00kapu/page/453">453–454, <span class="nowrap">456–</span>459, 461</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-471-45840-1</bdi>.</cite></span>

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<li id="cite_note-Johnson1989-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-Johnson1989_3-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFRobert_H._Johnson1989" class="citation book cs1">Robert H. Johnson (June 1989). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=HIFQAAAAMAAJ"><i>MVS: concepts and facilities</i></a>. Intertext Publications. p. 558. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-07-032673-6</bdi>.</cite></span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://www.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf#page=181">"Chapter 4. Executing Your Own Channel Programs"</a> <span class="cs1-format">(PDF)</span>. <a rel="nofollow" class="external text" href="https://www.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf"><i>z/OS Version 2 Release 4 DFSMSdfp Advanced Services</i></a> <span class="cs1-format">(PDF)</span>. IBM. August 2020. pp. <span class="nowrap">151–</span>210. SC23-6861-40.</cite></span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://www.bitsavers.org/pdf/ibm/360/os/R01-08/C28-6550-2_OSsysPrmg_Mar67.pdf"><i>IBM System/360 Operating System System Programmer's Guide</i></a> <span class="cs1-format">(PDF)</span>. IBM. March 1967. C28-6550-2.</cite></span>

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<li id="cite_note-Stotts1990-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Stotts1990_6-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFGary_A._Stotts1990" class="citation book cs1">Gary A. Stotts (1 August 1990). <i>DOS/VSE: Introduction to the Operating System</i>. QED Information Sciences. p. 18. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-89435-332-1</bdi>.</cite></span>

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<li id="cite_note-GC24-S037-12-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-GC24-S037-12_7-0">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/360/dos/GC24-5037-12_DOS_Supervisor_and_IO_Macros_Oct73.pdf"><i>DOS Supervisor and I/O Macros</i></a> <span class="cs1-format">(PDF)</span>. IBM. GC24-S037-12.</cite></span>

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<cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://publibfp.dhe.ibm.com/epubs/pdf/iesmge40.pdf"><i>IBM z/VSE Version 6 Release 1 System Macros User's Guide</i></a> <span class="cs1-format">(PDF)</span>. IBM. 2015. SC34-2709-00.</cite></span>

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<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://www.bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC28-6550-11_Data_Management_for_System_Programmers_Rel_21.7_Apr73.pdf#page=43">"Appendages"</a> <span class="cs1-format">(PDF)</span>. <a rel="nofollow" class="external text" href="http://www.bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC28-6550-11_Data_Management_for_System_Programmers_Rel_21.7_Apr73.pdf"><i>OS Data Management for System Programmers - Release 21</i></a> <span class="cs1-format">(PDF)</span>. IBM Systems Reference Library (Twelfth ed.). IBM Corporation. April 1973. p. 46. GC28-6550-ll<span class="reference-accessdate">. Retrieved <span class="nowrap">June 28,</span> 2022</span>.</cite></span>

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<li id="cite_note-FOOTNOTEDFSMSdfp199–200[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage229_EXCP_and_EXCPVR_Appendages]-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEDFSMSdfp199–200[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage229_EXCP_and_EXCPVR_Appendages]_10-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFDFSMSdfp">DFSMSdfp</a>, pp. 199–200, <a rel="nofollow" class="external text" href="https://www-01.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf#page=229">EXCP and EXCPVR Appendages</a>.</span>

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<li id="cite_note-FOOTNOTEDFSMSdfp201–202[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage231_The_Authorized_Appendage_List_(IEAAPP00)]-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEDFSMSdfp201–202[httpswww-01ibmcomserversresourcelinksvc00100nsfpageszOSV2R4sc236861fileidas300_v2r4pdfpage231_The_Authorized_Appendage_List_(IEAAPP00)]_11-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFDFSMSdfp">DFSMSdfp</a>, pp. 201–202, <a rel="nofollow" class="external text" href="https://www-01.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236861/$file/idas300_v2r4.pdf#page=231">The Authorized Appendage List (IEAAPP00)</a>.</span>

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<li id="cite_note-SoftwareAG-14"><span class="mw-cite-backlink">^ <a href="#cite_ref-SoftwareAG_14-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-SoftwareAG_14-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><cite id="CITEREFSoftware_AG" class="citation web cs1">Software AG. <a rel="nofollow" class="external text" href="https://documentation.softwareag.com/natural/nat825mf/ziip/naz-nat-processing.htm">"Natural zIIP Processing: TCBs, SRBs and Enclaves"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">Mar 22,</span> 2021</span>.</cite></span>

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<li id="cite_note-FOOTNOTES36084–121[httpbitsaversorgpdfibm360princOpsA22-6821-6_360PrincOpsJan67pdfpage87_Input/Output_Operations]-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTES36084–121[httpbitsaversorgpdfibm360princOpsA22-6821-6_360PrincOpsJan67pdfpage87_Input/Output_Operations]_16-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFS360">S360</a>, pp. 84–121, <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/360/princOps/A22-6821-6_360PrincOpsJan67.pdf#page=87">Input/Output Operations</a>.</span>

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<li id="cite_note-FOOTNOTES37013-45–13-46[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage396_CHANNEL_INDIRECT_DATA_ADDRESSING]-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTES37013-45–13-46[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage396_CHANNEL_INDIRECT_DATA_ADDRESSING]_17-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFS370">S370</a>, pp. 13-45–13-46, <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/370/princOps/GA22-7000-10_370_Principles_of_Operation_Sep87.pdf#page=396">CHANNEL INDIRECT DATA ADDRESSING</a>.</span>

</li>

<li id="cite_note-FOOTNOTES37013-38[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage389_CHANNEL-COMMAND_WORD]-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTES37013-38[httpbitsaversorgpdfibm370princOpsGA22-7000-10_370_Principles_of_Operation_Sep87pdfpage389_CHANNEL-COMMAND_WORD]_18-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFS370">S370</a>, p. 13-38, <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/370/princOps/GA22-7000-10_370_Principles_of_Operation_Sep87.pdf#page=389">CHANNEL-COMMAND WORD</a>.</span>

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<li id="cite_note-FOOTNOTES370-XA[httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage385_15-24-15-25][httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage384_Channel-Command_Word]-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTES370-XA[httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage385_15-24-15-25][httpbitsaversorgpdfibm370princOpsSA22-7085-1_370-XA_Principles_of_Operation_Jan87pdfpage384_Channel-Command_Word]_19-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFS370-XA">S370-XA</a>, p. <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/370/princOps/SA22-7085-1_370-XA_Principles_of_Operation_Jan87.pdf#page=#385">15-24-15-25</a>, <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/370/princOps/SA22-7085-1_370-XA_Principles_of_Operation_Jan87.pdf#page=384">Channel-Command Word</a>.</span>

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<li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><cite id="CITEREFIBM_Corporation1971" class="citation book cs1">IBM Corporation (August 1971). <a rel="nofollow" class="external text" href="http://bitsavers.org/pdf/ibm/dasd/2305/GA26-1589-2_2835_Storage_Control_and_2305_Fixed_Head_Storage_Module_Aug71.pdf"><i>Reference Manual for IBM 2835 Storage Control and IBM 2305 Fixed Head Storage Module</i></a> <span class="cs1-format">(PDF)</span>. p. 17<span class="reference-accessdate">. Retrieved <span class="nowrap">Dec 5,</span> 2019</span>.</cite></span>

</li>

</ol></div>

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</style><div id="OS/360_and_successors_I/O_access_methods71" style="font-size:114%;margin:0 4em"><a href="OS/360_and_successors" title="OS/360 and successors">OS/360 and successors</a> I/O <a href="Access_method" title="Access method">access methods</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Low-level</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul>

<li><a href="Execute_Channel_Program_in_Real_Storage" title="Execute Channel Program in Real Storage">EXCPVR</a></li>

<li><a href="Start_Input/Output" title="Start Input/Output">STARTIO</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Storage</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Network</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

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