Understand Mainframe Ecosystem

This page presents the mainframe ecosystem as a set of connected layers. A mainframe application is rarely only COBOL or only JCL: batch jobs start programs, programs call other programs, transaction managers expose online entry points, database and file technologies persist data, and utilities or schedulers move work around the platform.

The goal is to help read the analysis results as a system: source files, languages, middleware, data stores, utilities, and generated links all contribute to the same application graph.

Understand Mainframe Architecture

Start with the mainframe as a set of cooperating layers. Business logic is written in languages such as COBOL, PL/I, Assembler, JCL, Easytrieve or REXX. That logic is executed either by batch workloads or by online transaction managers, reads and writes persistent data, and is surrounded by security, scheduling, utility, printing, transfer and messaging services.

Mainframe

COBOL, COBOL Copybook, PL/I, JCL, Assembler, Easytrieve, REXX

Transaction Manager

Batch Subsystem

Relational

Hierarchical DB

Database

Data Files

Security

Scheduler

Sort and Dataset

Printing

Data Transfer

Messaging / Middleware

Architecture bucket	Taxonomy role	Technologies and artifacts to dispatch here	How to read this layer
Platform and runtime	Execution context	Priority 1: IBM z/OS / Enterprise COBOL, IBM i / AS400 / ILE COBOL, Micro Focus Visual COBOL, Micro Focus ACUCOBOL-GT, Micro Focus RM/COBOL, Micro Focus COBOL-IT, Fujitsu NetCOBOL, GnuCOBOL / OpenCOBOL, Veryant isCOBOL Priority 2: IBM z/TPF COBOL, IBM z/VSE COBOL, IBM z/VM COBOL, IBM COBOL for AIX, HPE NonStop COBOL / Tandem COBOL85 / ECOBOL, HPE NonStop Pathway / SCREEN COBOL, OpenVMS COBOL, Unisys ClearPath MCP COBOL, Unisys ClearPath OS 2200 COBOL, Stratus VOS / OpenVOS COBOL, HP 3000 / MPE COBOL, Bull / GCOS COBOL, Generic Micro Focus COBOL Priority 3: IBM MVS / OS/390 legacy COBOL, Fujitsu / Siemens BS2000 COBOL, ICL VME COBOL, NEC ACOS COBOL, Hitachi VOS3 COBOL, Wang VS COBOL, Data General AOS/VS COBOL, Prime / PRIMOS COBOL, NCR / AT&T UNIX COBOL, Honeywell / Multics COBOL, DEC PDP / RSTS / RSX COBOL, Microsoft COBOL / MS-COBOL, Realia COBOL / CA-Realia, Liant RM/COBOL, TinyCOBOL	The platform determines which parsers and ecosystem semantics can apply. IBM z/OS is the reference platform for full mainframe analysis. Priority `1` identifies the most common or most actionable runtimes; priority `2` identifies important enterprise runtimes that often need additional platform context; priority `3` identifies legacy, niche or site-specific runtimes.
Programming / templates	Source languages and reusable fragments	COBOL, COBOL copybook, PL/I, PL/I include, Assembler / HLASM, ALGOL, Easytrieve, REXX, CLIST, SAS, Natural, NOMAD, EGL, Focus, BMS maps	This is the application logic and shared declaration layer. It defines programs, includes, copybooks, generated-code patterns and reusable screen/map artifacts.
Transaction Manager	Online transaction processing	CICS, IMS/DC, TDS, CICS BMS, CICS transactions, CICS transient data queues, CICS SOAP/WSDL, CICS CTG	CICS and IMS/DC are central online entry-point layers. They introduce transactions, screens/maps, queues, services and transaction-to-program links.
Batch Subsystem	Batch orchestration	JCL, PROC, GCL, platform-specific command languages, job steps, DD statements	Batch ties the ecosystem together by launching programs and utilities, assigning datasets and creating execution chains.
Relational	SQL and relational DBMS access	Db2 for z/OS, Oracle gateways, embedded `EXEC SQL`, ProCOBOL, ProPL/I, SQL Analyzer artifacts	Db2 is the reference relational DBMS for z/OS COBOL and PL/I. SQL Analyzer can complement mainframe analysis for SQL artifacts.
Hierarchical DB	Hierarchical DBMS access	IMS DB / DL/I, TPFDF, DL/I calls such as `CBLTDLI`, `PLITDLI`, `AIBTDLI`, `CEETDLI`, `EXEC IMSSQL`	IMS DB may be used in batch, with IMS/DC, or with CICS. Links depend on program calls plus IMS structures such as PSB and DBD.
Database	Other DBMS families	IDMS, Datacom, ADABAS, DMSII, RDMS, Model 204, TOTAL, SUPRA, NOMAD database usage	Network, inverted-list and other DBMS families often require dedicated product, custom or UC/Labs coverage.
Data Files	Mainframe file storage	VSAM, GDG, QSAM, PDS, GSAM, BDAM, CICS files, file structures and JCL dataset declarations	File links often require combining program file declarations with JCL dataset declarations.
Security	Security services	RACF, ACF2, Top Secret, ICSF and security-related API or control usage	Security services explain access-control and cryptographic dependencies around programs, jobs and data.
Scheduler	Workload automation	CA-7, Control-M, TWS, ESP, CA-11, Zeke, OpCon	Schedulers describe when jobs run and how job streams depend on each other.
Sort and Dataset	Dataset and utility operations	SORT, IDCAMS, IEBGENER, DFSORT, compiler/link-edit utilities, control cards	Utility layers explain technical transformations, dataset management and build/runtime preparation steps.
Printing	Output management	StreamWeaver and related print/output utilities	Printing utilities explain report and output-production flows.
Data Transfer	External movement	FTP, NDM, Co:Z, sockets and transfer utilities	Transfer utilities explain external data movement into or out of the mainframe estate.
Messaging / Middleware	Asynchronous and service integration	IBM MQ, data queues, CICS services, CICS socket, CICS SOAP, CTG	MQ calls and CICS service calls create integration edges beyond pure program-to-program calls.

Identify the Core Languages

The language layer is the base of the ecosystem. It tells CAST what kind of source file is being read, which analyzer or extension can process it, and which syntax rules can create objects and links.

Language or artifact	Role in the ecosystem	Common relationships	CAST Profiler	CAST Imaging
COBOL	Main business-programming language for batch and online workloads	Calls programs, reads/writes files, embeds SQL, uses CICS, IMS, MQ	✓	Product `com.castsoftware.mainframe`
COBOL copybook	Included COBOL fragment, usually data structures or shared declarations	Included by COBOL programs; shapes file and data layouts	✓	Product `com.castsoftware.mainframe`
JCL	Batch orchestration and execution language	Defines jobs, steps, DD datasets, utilities, program starts	✓	Product `com.castsoftware.mainframe`
PL/I	Business and system programming language often connected to Db2, IMS, MQ, files	Calls programs, embeds SQL, uses DL/I and MQ APIs	✓	Product `com.castsoftware.pl1`
Assembler / HLASM	Low-level system and high-performance application code	Can participate in JCL, Db2, CICS, IMS, and utility flows depending on patterns	✓	Product `com.castsoftware.asmzos`
Easytrieve	Reporting and batch-oriented 4GL	Often reads files or SQL data and participates in batch chains	✓	Product `com.castsoftware.easytrieve`
REXX	Scripting around TSO, automation, and utilities	Can invoke commands, utilities, or operational scripts	✓	Product `com.castsoftware.rexx`
CLIST	Command scripting around TSO and operational automation	Can invoke commands, utilities, or operational scripts	✓	UC/Labs CLIST
Natural	4GL commonly associated with ADABAS	Connects application logic to ADABAS/Natural ecosystems	✓	UC/Labs Natural / ADABAS
SAS	Analytical and reporting ecosystem	Usually requires dedicated or custom extension coverage	✓	UC/Labs SAS
Focus	Reporting and 4GL ecosystem	Usually requires dedicated or custom extension coverage	✓	UC/Labs Focus
NOMAD	4GL and database-oriented ecosystem	Usually requires dedicated or custom extension coverage	✓	UC/Labs NOMAD
EGL	Generated-code and 4GL ecosystem	May generate or connect to COBOL/mainframe-style assets depending on the application	✓	Product `com.castsoftware.egl`
Eagle88	Specialized legacy language ecosystem	Usually requires dedicated or custom extension coverage	✓	UC/Labs Eagle88
ALGOL	Legacy system and workflow language, especially in Unisys MCP / ClearPath contexts	Can implement workflows, system procedures, command layers or application services depending on the platform	✓	Custom / UA ALGOL

COBOL Platform Support

COBOL support depends on the platform and compiler dialect. IBM z/OS is the reference case for full mainframe ecosystem analysis, while other platforms may keep COBOL parsing but lose screen, transaction, DML or platform-specific semantics.

The table follows the platform/runtime inventory above. Qualification means the runtime should be identified during onboarding, but the documented support level must be confirmed from source samples, compiler options and ecosystem layers before committing to analysis scope.

Platform / Runtime	COBOL dialect	CAST Profiler	CAST Imaging	Qualification note
IBM z/OS / Enterprise COBOL	Enterprise COBOL for z/OS, up to v6	✓	Very High	Reference case for CAST Imaging.
IBM i / AS400 / ILE COBOL	COBOL/400, ILE COBOL	✓	High	Some screen and transaction constructs are not taken into account.
Micro Focus Visual COBOL	Micro Focus COBOL	-	High	Screen-related definitions and statements are not supported.
Micro Focus ACUCOBOL-GT	ACUCOBOL-GT	-	Medium	Screen-related definitions and statements are not supported.
Micro Focus RM/COBOL	RM/COBOL	-	Qualification	Confirm compiler compatibility and copybook behavior from source samples.
Micro Focus COBOL-IT	COBOL-IT	-	Qualification	Treat as a Micro Focus-style dialect candidate, but validate directives, copy paths and screen syntax.
Fujitsu NetCOBOL	NetCOBOL	-	Qualification	Validate dialect options and platform-specific runtime calls before analysis.
GnuCOBOL / OpenCOBOL	GnuCOBOL, OpenCOBOL	-	Qualification	Usually direct source delivery; confirm copybook syntax, preprocessing and extensions.
Veryant isCOBOL	isCOBOL	-	Qualification	Validate runtime libraries, GUI/screen usage and dialect extensions.
IBM z/TPF COBOL	z/TPF COBOL	-	Qualification	COBOL may coexist with Assembler and C/C++; transaction and TPFDF context must be qualified separately.
IBM z/VSE COBOL	z/VSE COBOL	-	Qualification	Close to IBM mainframe COBOL, but platform services and job control differ from z/OS.
IBM z/VM COBOL	z/VM COBOL	-	Qualification	Confirm source format, runtime context and batch/control language before delivery.
IBM COBOL for AIX	IBM COBOL for AIX	-	Qualification	Non-z/OS runtime; qualify compiler directives, copy paths and database/file context.
HPE NonStop COBOL / Tandem COBOL85 / ECOBOL	HP COBOL for TNS/E Programs, COBOL85, ECOBOL	-	Medium	Transactions and screens are not supported; some CICS/IMS, file descriptor and SORT/MERGE rules may produce false violations.
HPE NonStop Pathway / SCREEN COBOL	SCREEN COBOL, Pathway context	-	Medium	COBOL can be parsed, but Pathway and screen semantics require careful qualification.
OpenVMS COBOL	HP COBOL for OpenVMS	-	Medium	Copy directive and COBOL 85 syntax are supported.
Unisys ClearPath MCP COBOL	Unisys COBOL	-	No	Existing qualification notes indicate copybook inclusion and program calls are not correctly managed for Unisys A Series style COBOL.
Unisys ClearPath OS 2200 COBOL	Unisys OS 2200 COBOL	-	Qualification	Qualify dialect, copy/include behavior, workflows and DBMS context; do not assume z/OS semantics.
Stratus VOS / OpenVOS COBOL	VOS COBOL	-	Medium	Some constructs may need to be removed to avoid parsing issues.
HP 3000 / MPE COBOL	MPE COBOL	-	Qualification	Qualify copy/include syntax, file system semantics and job/control language separately.
Bull / GCOS COBOL	GCOS COBOL	-	Low	DML, screens and transactions are not supported; some constructs may need to be removed.
Generic Micro Focus COBOL	Micro Focus COBOL	-	High	Use when the exact Micro Focus runtime is unknown; confirm directives and screen usage.
IBM MVS / OS/390 legacy COBOL	IBM COBOL for OS/390, VS COBOL II	✓	Medium	Source code can be analyzed with CAST Imaging.
Fujitsu / Siemens BS2000 COBOL	BS2000 COBOL	-	Qualification	COBOL exists, but openUTM, SDF/SDF-P and UDS/SQL context differ from z/OS.
ICL VME COBOL	VME COBOL	-	Qualification	Qualify dialect, TP monitor, DBMS and command language before analysis.
NEC ACOS COBOL	ACOS COBOL	-	Qualification	Legacy/site-specific dialect; validate parser behavior on representative samples.
Hitachi VOS3 COBOL	VOS3 COBOL	-	Qualification	Legacy/site-specific dialect; validate compiler directives and platform calls.
Wang VS COBOL	Wang VS COBOL	-	Qualification	Legacy/site-specific dialect; direct source samples are required for scope decisions.
Data General AOS/VS COBOL	AOS/VS COBOL	-	Qualification	Legacy/site-specific dialect; qualify copy/include and file semantics.
Prime / PRIMOS COBOL	PRIMOS COBOL	-	Qualification	Legacy/site-specific dialect; validate source format and runtime APIs.
NCR / AT&T UNIX COBOL	UNIX COBOL	-	Qualification	UNIX COBOL family; qualify compiler, directives and database/file context.
Honeywell / Multics COBOL	Multics COBOL	-	Qualification	Legacy/site-specific dialect; qualify source format and ecosystem dependencies.
DEC PDP / RSTS / RSX COBOL	DEC COBOL	-	Qualification	Legacy/site-specific dialect; validate parser behavior on source samples.
Microsoft COBOL / MS-COBOL	MS-COBOL	-	Qualification	Distinguish from COBOL .NET, which is not supported as Object COBOL.
Realia COBOL / CA-Realia	Realia COBOL	-	Qualification	Validate directives, copybook handling and generated/runtime conventions.
Liant RM/COBOL	RM/COBOL	-	Qualification	Validate dialect level and runtime-specific constructs from source samples.
TinyCOBOL	TinyCOBOL	-	Qualification	Usually small or niche codebases; validate source compatibility before scope confirmation.
Windows	COBOL .NET	-	No	Object COBOL is not supported.

Some quality rules specifically target IBM-style COBOL. When a different compiler is used, especially Micro Focus or non-z/OS dialects, rule results should be interpreted with that platform context in mind.

Batch Support

Batch support is platform-specific. In the CAST Imaging Mainframe scope, batch support means IBM z/OS JCL and PROC analysis. IBM i / AS400 uses CL/CLP instead of JCL; CL is strongly supported and detected through the IBM i / midrange analyzers, not through the z/OS JCL parser. Other platforms may have batch-control languages or job-control concepts, but they are not handled by the same parser.

Platform / OS	Control language	CAST Profiler	CAST Imaging	Qualification note
IBM zSeries / z/OS	JCL	✓	Very High	Main supported batch-control language for CAST Imaging Mainframe scope.
IBM i / AS/400	CL / CLP	✓	High	CL/CLP is covered through IBM i / midrange analyzers, not the Mainframe JCL analyzer.
Unisys A Series	Workflow	-	No	No product support.
Bull DPS7 / DPS8	JCL	-	No	No product support.
Tandem / HP	JCL	-	No	No product support.

Understand How Layers Connect

Use this shifted matrix as a quick reading guide for common mainframe interconnections. Read the layer first, then follow each green check to identify likely relationships across language or artifact families.

Architecture layer	COBOL	Copybooks	JCL / PROC	PL/I	Assembler	Easytrieve / 4GL	REXX / CLIST	CICS / IMS / Scheduler definitions
Batch	✓	✓	✓	✓	✓	✓	✓	✓
Online transactions	✓	✓	-	✓	✓	✓	-	✓
Program calls	✓	-	✓	✓	✓	✓	✓	✓
Relational DB	✓	✓	-	✓	✓	✓	-	-
IMS DB	✓	✓	✓	✓	✓	-	-	✓
Files / datasets	✓	✓	✓	✓	✓	✓	✓	✓
Messaging	✓	-	-	✓	✓	-	-	✓
Utilities / operations	✓	-	✓	✓	✓	✓	✓	✓

Place the Platform in Context

IBM z/OS is the primary platform for the documented mainframe analyzer scope, with JCL, COBOL, PL/I, CICS, IMS, Db2, VSAM, MQ and related utilities forming the most common ecosystem.

Other platforms often need a more careful reading:

Other Platforms

IBM z/TPF COBOL
IBM z/VSE COBOL
IBM z/VM COBOL
IBM COBOL for AIX
HPE NonStop COBOL / Tandem COBOL85 / ECOBOL
HPE NonStop Pathway / SCREEN COBOL
OpenVMS COBOL
Unisys ClearPath MCP COBOL
Unisys ClearPath OS 2200 COBOL
Stratus VOS / OpenVOS COBOL
HP 3000 / MPE COBOL
Bull / GCOS COBOL
Generic Micro Focus COBOL

IBM MVS / OS/390 legacy COBOL
Fujitsu / Siemens BS2000 COBOL
ICL VME COBOL
NEC ACOS COBOL
Hitachi VOS3 COBOL
Wang VS COBOL
Data General AOS/VS COBOL
Prime / PRIMOS COBOL
NCR / AT&T UNIX COBOL
Honeywell / Multics COBOL
DEC PDP / RSTS / RSX COBOL
Microsoft COBOL / MS-COBOL
Realia COBOL / CA-Realia
Liant RM/COBOL
TinyCOBOL

Platform family	What changes
IBM z/OS and legacy MVS / OS/390	This is the reference ecosystem for full CAST Imaging Mainframe scope: Enterprise COBOL, JCL, CICS, IMS, Db2, VSAM, MQ, schedulers and PDS/PDSE delivery patterns. Older IBM COBOL for OS/390 or VS COBOL II can still be analyzed, but should be qualified as legacy dialects.
IBM i / AS400	COBOL/400 and ILE COBOL can be present, but the surrounding ecosystem is not z/OS. Expect CL/CLP instead of JCL, source physical files instead of PDS dumps, Db2 for i, DDS and IBM i library/object conventions.
IBM z/TPF	High-volume transaction processing, historically Assembler-heavy, now with more C/C++ and COBOL. Linux-like build concepts may appear, transaction routing is specific, and TPFDF introduces a specialized database layer.
IBM z/VSE and z/VM	COBOL may look close to IBM mainframe COBOL, but operating services, job/control language, deployment conventions and runtime context differ from z/OS. Confirm source format and execution model before assuming z/OS patterns.
IBM COBOL for AIX	COBOL runs outside the classic mainframe environment. Qualification should focus on compiler directives, copybook paths, database access, filesystem conventions and scripts used to build or launch programs.
Micro Focus family	Visual COBOL, ACUCOBOL-GT, RM/COBOL, COBOL-IT and generic Micro Focus COBOL often preserve COBOL syntax while moving runtime, screens, files and deployment outside z/OS. Screen definitions, directives, copy paths and runtime libraries need explicit qualification.
Fujitsu NetCOBOL, Veryant isCOBOL, GnuCOBOL / OpenCOBOL	These are usually distributed or migrated COBOL runtimes. Direct source delivery is more common than PDS dumps, and ecosystem links depend on scripts, database files, middleware and runtime configuration.
HPE NonStop / Tandem	COBOL, COBOL85, ECOBOL and SCREEN COBOL may appear with Pathway, NonStop SQL, TAL/SPL/C/C++ and platform-specific services. Transaction and screen semantics should be qualified separately from COBOL parsing.
OpenVMS COBOL	COBOL source can be present with OpenVMS copy directives, command procedures and platform-specific file conventions. Batch and operational context should not be read as z/OS JCL.
Fujitsu / Siemens BS2000 and ICL VME	COBOL exists, but TP monitors, command languages and DBMSs differ from z/OS. openUTM, SDF/SDF-P, UDS/SQL, LEASY or AVAS may appear instead of CICS, JCL or Db2 patterns.
Unisys ClearPath MCP / OS 2200	COBOL dialects, command/workflow layers and DBMS layers differ; ALGOL may be important, and DMSII or RDMS are examples from the DBMS landscape. Do not assume z/OS copybook, JCL or transaction semantics.
Stratus VOS / OpenVOS, HP 3000 / MPE, Bull / GCOS	COBOL-like or mainframe-style systems may appear, but platform APIs, file systems, transaction layers and DBMSs can diverge strongly from IBM z/OS. Some constructs may require removal or custom qualification before parsing.
Other legacy or niche COBOL runtimes	NEC ACOS, Hitachi VOS3, Wang VS, Data General AOS/VS, Prime / PRIMOS, NCR / AT&T UNIX COBOL, Honeywell / Multics, DEC PDP / RSTS / RSX, Microsoft COBOL, Realia / CA-Realia, Liant RM/COBOL and TinyCOBOL should be treated as sample-driven qualification cases. First confirm dialect, compiler options, copy/include behavior, file semantics and available surrounding artifacts.