How CMS Files Are in
File Status rabIes • Chain Links. . • • • . • • • 2- 86 • • • • 2- 86 • 2- 87 CMS Record Formats • . • • • • • 2- 88 Disk ••.•• Physical Organization of Virtual • 2-88
Disks • • • • • • • • • • • •• 2-88
The Master File Directory ••••.. 2-89 Keeping rrack of Read/Write Disk
Storage: QMSK and QQMSK •••••• 2-90 Dynamic Storage Management: Active
Disks and Files •••••••.•• 2-93 CMS Routines Used To Access the File System. • • • ••••••••••• 2-93
Access a Virtual Disk: DMSACC •••• 2-93
Handling IIO Operations. • • • • 2-94 Unit Record I/O Processing • • 2-94 Han.dlin;, Interruptions •••••••• 2- 98
Disk 1/0 in CMS. • • • • 2- 98 Read or Write Disk I/O •• 2-98 Managin] eMS _ .•.•• 2-99 Types of Allocated Free Storage ••• 2-99 Free Storage Management Pointers. • • ••••••••••• 2-100 DMSFREE Free Storage Pointers •••• 2-101 DMSFRS Method of Operation.. .2-104 Relative Efficiency of DMSFREE Requests. • • • • • • • • • • .2-105 Releasing Allocated Storage ••••• 2-105 DMSFRE Service Routines. • .2-105 Stora;,e Protection Keys. • • • • • .2-107 CMS System Handling of PSW Keys ••• 2-107 CP Handling for Saved Syste.s •••• 2-108 Error Codes from DMSFRRF., DMSFRES, and DMSFRET • • • • • .2-110 The DMSFRES Macro. • • .2-111
The DMSKEY Macro.. • ••••• 2-111
The DMSEXS Macro. • • •• 2-112 SIMULATE NON-CMS OPERATING ENVIRONMENTS ••••••••••••• 2-113
Access Method Support for Non-CMS Operating Environments •••••••• 2-113 OS Access Method Support •••••• 2-113 CMS Support for the Virtual Storage Access Method •••••••••••• 2-114
Creating the DOSCB Chain •••••• 2-114
Executing an AMSERV Function ••••• 2-114
Executing a VSAM Function for a DOS User. • • • • • • • • .2-116 CMS/DOS SVC Handling •••••••• 2-116
Executing VSAM Function for an as User. • . • • • • • . . • . . . .2-118 Completion processing for OS and DOS VSAr. Programs •..•••••. 2-121 OS Simulation by CMS ••.•.•.•. 2-122 Simulating a DOS Environment under eMS ••••••••••••••••• 2-137
Initializing DOS and Processing DOS System Control Commands •••••• 2-137 Setting or System Environment Options •••••••• 2-139 Process CMS/DOS OPEN CLOSE Functions ••••••••••••• 2-140 Process CMS/DOS Exe=ution-Related Control Commands •••••••••• 2-142 Simulate DOS SVC Functions ••••• 2-144 SV:s Tredted as No-Op by CMS/DOS •• Process CMS/DOS sarvice .Commands •• 2-148
Terminate processing the CMS/DOS Environment • • • • • • .2-148 PERFORMING MISCELLANEOUS CMS FUN:TIONS • . • • • • eMS 3atch Facility •• Error Printouts. • • • • • .2-149 • • .2-149 • •••••• 2-153
C MS DI RECl'ORI ES. • • .2-155 MODULE ENTRY POINT DIRECTORY. • .2-157 CROSS REFERENCE •••• 2-169 LABEL-TO-MODULE CROSS REFERENCE •••• 2-189 CMS DIAGNOSTIC AIDS. • .2-237 SUPPORTED DEVICES. • • • .2-239 DMSFREX CODES. • • • • .2-240 Error :odes from DMSFREE, DMSFRES, and DMSFRET • • • • .2-240 ABEND CODES. • ••••••••• 2-241
Abend Recovery ••••••• 2-241
Unrecoverable Termination --The
HALT Option of DMSERR • • • • .2-242 APPENDIX A: CMS MACRO LIBRARY • .2-241 APPENDIX E: CMS/DOS Macro Library ••• 2-251 INDEX. • .2-253
vi IBM VM/370 System Logic and Program Determination--Volume 2

Figure 1.
FiJure 2.
Figure 3. Figure 4. Fi;Iure 5.
Figure 6.
Figu:r:e 7. Figure 8.
I'igure 9.
Figure 10. Figure 11. Figure 12.
Figure 13.
Figure 14. CftS File System ••••••••••••• 2-6
Devices Supporte1 by a virtual 5achine •••••••••••• 2-13 CftS Storage ftap •••••••••••• 2-16 CftS (and Request; processing ••••••••••••••••• 2-30 PSi Fields when :alled Routine Starts ••••••••••••• 2-31
Register Conte&ts when :alled
Routine Starts ••••••••••••• 2-31 Simulated os Supervisor Calls ••••••••••• __ .========2-31 An Overview of the Functional
Areas CKS ••••••••••••••• 2-52
Details of CftS Systea Functions and the Routines that
Perform Them ••••••••••••••• 2-53 PSi Fields when Callea Routine is Started ••••••••• 2-69
Register Contents when :alled Routine is Started ••••••••• 2-10 How CMS File Records are
Chained Togehter ••••••••••• 2-86
Format of a File Status Block; Format of a rile Status rable •••••••••••••••••••••• 2-86
For.at of the First Chain
Link and Nth Links ••• 2-89 15.
Figure 16.
Figure 17. Figure 18. Figure 19. FIGURES of Fixed-Length Recoras and Variable-Length Re=oris in Files ••••••••••• 2-B9
structure of the Master File Directort ••••••••••••• 2-92
Disk Storage Allocation Using the QMSK Data Block •••••••• 2-92
Flow of Control for Unit Recora I/O processing •••••• 2-94
Relationships in storage
between the CMS Interface and the CMSAMS ana CHSVSAM DCSSs •••••••••••••••••••• Figure 20. The Relationships in storage between the User Program and the ana CMSVSAft DCSSs ••••••••• 2-111
Figure 21. Relationship in storage
between the User Program, the os Simulation and
Interface Routines, and the CMSDOS ana CMSVSAft DCSSs •• 2-118 figure 22. OS Functions that CMS Simulates ••••••••••••••••• 2-123
Figure 23. Devices Supported by a Virtual Machine ••••••••••• 2-239
Figure 24. CBS Abend Codes ••••••••••• 2-243 Contents vii