Don't Wait for Migration: How to Access Mainframe Data Today – A Guide for IT Leaders

The Data Your Business Runs On Is Harder to Reach Than It Should Be

Enterprises running IBM mainframes aren’t doing so by accident. These systems process millions of transactions every day across vital enterprises like banking, insurance, healthcare, and government. The data they hold is irreplaceable: customer records, account histories, policy details, and transaction logs built up over decades.

The problem is access. That data is locked behind formats and protocols that most modern developers have never encountered and the specialists who built these systems are retiring faster than organizations can replace them.

An estimated 70% of business-critical enterprise data still resides on mainframes (IBM, 2023). Digital transformation initiatives stall not because the data doesn’t exist, but because accessing it requires deep, specialized knowledge that organizations can no longer afford to wait on.

VSAM Files: Where Data Access Breaks Down

VSAM files, the mainframe’s primary storage format, are one of the most common places where data access breaks down. A single VSAM cluster can contain multiple interleaved record types, each with different structures defined through COBOL REDEFINES statements. Without the correct copybook and the expertise to interpret it, the raw data is unreadable: a wall of EBCDIC-encoded bytes with no obvious structure.

This is the hidden cost of inaccessible data: not a technical curiosity, but a strategic bottleneck. The records that drive your business are there, they’re just not in a form your modern teams can work with.

A Third Path: Make the Data Accessible Where It Lives

The mainframe modernization conversation has been stuck between two costly extremes for decades. Rip-and-replace, migrating everything off the mainframe, is expensive, high-risk, and frequently unsuccessful. Leaving it alone accumulates technical debt and integration bottlenecks that get harder to unwind every year.

CoreIQ, OpenLegacy’s enterprise mainframe platform, offers a third path: expose the data through modern interfaces without moving it. The mainframe stays in place. The data stays where it is. What changes is how your organization interacts with it.

How CoreIQ Turns VSAM Data Into a REST API In Minutes

Working with complex VSAM files used to require deep mainframe expertise and weeks of custom integration work. CoreIQ streamlines that through a guided workflow executed entirely from a browser.

1. Sample the Data Intelligently

CoreIQ connects to your mainframe and retrieves data samples from across the entire VSAM dataset not just the first few records. Because KSDS data clusters by key, pulling only the top rows can hide important structural variation. CoreIQ’s sampling approach surfaces the full complexity of the file before any decisions are made.

2. Match the Right Copybook Automatically

CoreIQ intelligently suggests the best-fit data model based on record length, automatically matching your data against candidate copybook structures. For files with REDEFINES statements, it scans related system resources directly on the mainframe to find matching definitions, eliminating the manual search that once consumed days of specialist time.

3. Resolve Ambiguous Structures Visually

COBOL REDEFINES is the mainframe equivalent of a union type, where the same byte range can mean different things depending on context, but there’s rarely an explicit field to tell you which interpretation applies. CoreIQ provides intuitive dropdowns to switch between alternative structures, letting users visually confirm which interpretation matches the actual data without writing a line of code.

4. Validate Every Record Layout

CoreIQ’s auto-matcher doesn’t just parse, it validates. The algorithm explores every REDEFINES branch, checks binary data against field-level COBOL rules, and ranks surviving layouts by specificity. The result is a per-record, verified interpretation, not a guess.

5. Publish as a REST API

Once data structures are defined and approved, they can be published to the OpenLegacy Hub as reusable modules. The output is a fully functional REST API that any modern application uch as cloud-native, mobile, or web can consume without any knowledge of what’s running underneath.

What IT Leaders Need to Know About Security and Compliance

CoreIQ works within your existing mainframe security model with no changes required, nothing bypassed.

• The data never leaves the mainframe. CoreIQ reads and decodes it; no migration or replication is required.
• Every user authenticates with their own mainframe credentials. RACF, ACF2, and Top Secret rules apply exactly as they do today.
• CoreIQ never stores passwords. Credentials are AES-256-GCM encrypted in browser session cookies only and never written to disk.
• Every operation is executed under the individual user’s identity. No shared service accounts. Full audit trail preserved.

Developers consuming the resulting REST APIs don’t need any knowledge of COBOL, EBCDIC, or mainframe protocols. The complexity is abstracted but the security is not.

Accessing What the Mainframe Stores and What It Does

VSAM is one of the most complex data access challenges CoreIQ addresses, but it is not the only one. Modern applications often need two things from the mainframe: the data it holds, and the business logic it runs. CoreIQ provides a path to both — accessible from a browser, without requiring specialist tooling for each system.

Accessing the Data the Mainframe Stores

Beyond VSAM, CoreIQ connects to the other storage systems where mainframe data commonly lives:

• DB2, IMS-DB, and AS/400 databases: query and browse structured data with pagination and schema visibility, without a dedicated database client.
• Datasets and PDS members: browse, view, and edit COBOL source, JCL scripts, and copybooks directly, removing the need for terminal access to inspect or update source files.
• Record layout catalogs: organize and manage data model associations across systems in a centralized catalog, so definitions built once can be reused across integrations.

Accessing the Business Logic the Mainframe Runs

Much of what the mainframe does isn’t stored data, it’s active processes. Account updates, policy calculations, transaction processing: these run as CICS transactions or batch jobs. Modern applications that need to trigger or consume those processes face the same access problem as data. CoreIQ addresses this too:

• CICS transactions: execute and test transactions via OL-CICS or CTG, with copybook-driven buffer population so teams can interact with mainframe programs without writing transaction-layer code from scratch.
• Batch jobs: submit JCL, monitor active jobs, and view spool output, giving teams visibility into scheduled mainframe processing without requiring a dedicated operations console.

Frequently Asked Questions

Can I access mainframe data without a mainframe specialist?

Yes. CoreIQ is designed so that the teams doing the integration work and the developers consuming the resulting APIs do not need COBOL or mainframe expertise. The platform handles data decoding, structure matching, and protocol translation, exposing the output as standard REST APIs that any modern development team can work with.

Do I have to migrate off the mainframe to modernize?

No. CoreIQ connects to the mainframe where it runs and exposes its data and business logic through modern APIs without moving or replicating anything. The mainframe continues to operate as-is. What changes is how your other systems and teams interact with it.

Can VSAM data be converted to a REST API?

Yes. CoreIQ reads the VSAM dataset, matches the data against copybook structures, resolves complex REDEFINES definitions through a guided visual workflow, and publishes the confirmed layout to the OpenLegacy Hub as a reusable REST API endpoint. The process requires no COBOL expertise and is completed entirely through a browser.

Will this affect our existing mainframe security controls?

No. CoreIQ operates within your existing mainframe security model. Each user authenticates with their own credentials, RACF/ACF2/Top Secret rules are enforced as normal, and no passwords are stored by the platform. Your audit trail remains intact.

The Bottom Line

The path from mainframe to cloud is real. But for most enterprises it is a multi-year journey, and for the foreseeable future the mainframe remains at the center of critical operations. The need to modernize, however, is immediate. Waiting until the migration is complete is not a strategy; it is a bottleneck.

CoreIQ answers that question by meeting the mainframe where it is: decoding its data formats, respecting its security model, and exposing its assets through the interfaces modern teams expect.

Watch CoreIQ in action or contact us to learn more about CoreIQ