Second Edition (March 1979) is a .ajor revision of and obsoletes 5Y20-0886-0 and lewsletters 5125-0446 and SI25-0467. edition, 5Y20-0886-1, corresponds to Release 6 PLC 1 (progra. Level Change) of the IBB Virtual Bachine PacilitYl370 and to all subsequent releases until otherwise
indicated in new editions or lewsletters. changes and additions to text and illustrations are indicated by a vertical bar to the left of the change.
Changes are periodically .ade to the infor.ation herein; before using
this publication in connection with the operation of IBB syste.s,
consult the latest IB! Syste./31Q Bibliography, Order 10. GC20-0001, for
the editions that are and current.
Publications are not stocked at the address given below; requests for
copies of IBB publications should be .ade to your IBB representative or
to the IBB branch office serving your locality. 1 for. for readers' co •• ents is provided at the back of this
publication. If the for. has been re.oved, co •• ents .ay addressed to IBB Corporation, 'B/370 Publications, Dept. D58, Bldg. 706-2, P.O. Box 390, Poughkeepsie, lew York 12602. IB! .ay use or distribute any of the
infor.ation you supply in any way it believes appropriate without
incurring any obligation whatever. You .ay, of course, continue to use
the infor.ation you supply. © Copyright International Business !achines Corporation 1977, 1979

Tbis publication provides the IBM system
bardware and software support personnel
with the infor.ation needed to analyze problems that may occur on the IBM Virtual Machine Facility/370 (VM/370). Tbis .anual comprises three volumes: "Volume 1. VM/370 Control Program (CP)," "Volume 2. Conversational Monitor System (CMS)," and "Volume 3. Remote Spooling Communications Subsystem (RSCS)" contain
tbe logic description for each of the
components. Each of these volumes is
divided into four sections: Introduction, Method of Operation, Directory, and
Diagnostic Aids.
The Method of operation and prograM organization sections contain the functions
and relationsbips of the program routines
in VM/370. They indicate the program operation and organization in a general way to serve as a guide in understanding VM/370. They are not meant to be a
detailed analysis of VM/370 programming and
cannot be used as such.
The directories contain descriptions of
all the assemble modules in CP, CMS, and RSCS@ They also contain extensive
cross-references between modules and labels
within a VM/370 component.
The diagnostic aids sections contain
additional information useful for determining tbe cause of a problem. Appendix A, located in Volume 1,
contains a description of V!j370 Extended
Control-program Support (ECPS). Appendix B, also located in Volume 1,
describes VM/370 support for the IBM 3850 Mass Storage System (MSS). • Isolate the component of V8/370 in which
the problem occurred. • Use the list of restrictions in !!L170 A§§§Ag§§ to be certain that the
operation that was being performed vas
valid.
Preface • Use the directories and use the VM/31Q And Contr.Ql Logic to
help you to isolate the problem. • Use the method of operation and program
organization sections, if necessary, to
understand the operation tbat was being
performed. TERMINOLOGY The following terms in tbis publication
refer to the indicated support devices: • "2305" refers to IB! 2305 Fixed Head Storage, Models 1 and 2. • "270x" refers to IB! 2701, 2702, and 2703 Transmission Control Units or the
Integrated Communications Adapter (ICA) on the System/370 Bodel 135. • "3330" refers to tbe IB! 3330 Disk Storage, Models 1, 2, or 11; the IEM 3333 Disk Storage and Control, Models 1
or 11; and tbe 3350 Direct Access Storage operating in 3330/3333 Model 1
or 3330/3333 !odel 11 compatibility
mode. • • • • • • "3340" refers to tbe IBM 3340 Disk Storage, Models A2, B1, and B2, and the
3344 Direct Access Storage Model B2. "3350" refers to the IBM 3350 Direct
Access Storage !!odels 12 and B2 in
native mode. "3704", "3705", or "3701" refers to IBM Communica tions 3704 and 3705 Controllers.
The term "3705" refers to the 3705 I and
the 3705 II unless otberwise noted.
"2741" refers to the IBM 2741 and the
3767, unless otherwise specified. "3270" refers to a series of display
devices, namely the IBM 3275, 3276,
3277, 3278 Display Stations. 1 specific
device type is used cnly when a
distinction is required between device
types.
Information about display terminal usage
also applies to the IBM 3036, 3138, 3148,
and 3158 Display Consoles when used in
display mode
6 unless otherwise noted. Preface iii