Mainframe modernization or emulation services

Data as of Oct 15, 2026Reviewed by

How we measure

Which brands AI mentions

#BrandMentioned in
1AWS Transform82%
2Rocket Software58%
=3IBM Z42%
=3OpenText33%
=3LzLabs31%

Mentioned in · Jul 5 – Oct 15, 2026

ChatGPT SearchChatGPT SearchGoogle AI ModeGoogle AI Mode

Widest split: IBM Z, 65% on ChatGPT Search and 18% on Google AI Mode.

  • 1AWS TransformChatGPT Search 70%Google AI Mode 95%
  • 2Rocket SoftwareChatGPT Search 61%Google AI Mode 55%
  • =3IBM ZChatGPT Search 65%Google AI Mode 18%
  • =3OpenTextChatGPT Search 30%Google AI Mode 36%
  • =3LzLabsChatGPT Search 35%Google AI Mode 27%

Questions and answers

  • Google AI ModeOct 15, 2026

    1. 1AWS
    2. 2Micro Focus
    3. 3TmaxSoft
    4. 4Rocket Enterprise Suite
    5. 5Rocket Software
    6. 6OpenText
    7. 7Heirloom Computing
    8. 8JBoss
    9. 9AWS Transform
    10. 10TmaxSoft OpenFrame
    11. 11Rocket Visual COBOL

    Ensuring high availability (HA) for legacy mainframe applications depends heavily on whether you choose rehosting/emulation (lifting and shifting via a runtime environment) or refactoring/rewriting (converting code to Java/C# for cloud-native elasticity).

    The industry features several top-tier modernization and emulation platforms tailored for high availability and enterprise continuity:

      • AWS Mainframe Modernization: A managed cloud service on AWS Mainframe Modernization that supports both rehosting (using Micro Focus or Blu Age engines) and refactoring. It automates deployment, scaling, and high-availability setups across multi-az AWS infrastructure.
      • OpenFrame by TmaxSoft: A widely used rehosting solution that moves legacy COBOL, PL/I, and JCL assets to Linux/Unix/Windows or cloud environments. It mimics the IBM z/OS environment closely while enabling native active-passive or active-active high-availability clustering.
      • Rocket Enterprise Suite: Offered by Rocket Software , this suite provides hybrid integration, data access, and application modernization tools that allow legacy systems to interface securely with modern cloud HA architectures without a total rewrite.
      • Micro Focus (now part of OpenText) Visual COBOL / Enterprise Server: An industry benchmark for emulation and rehosting. Enterprise Server provides built-in workload management, scalability, and failover capabilities to guarantee high availability when moving off physical mainframes.
      • Heirloom Computing: Specializes in refactoring legacy COBOL/PL/I applications directly into standard Java workloads that run natively on cloud application servers (like Tomcat or JBoss), inheriting enterprise cloud high availability automatically.

    To help narrow down the best path for your organization, please share:

    • Are you looking to rehost/emulate as-is, or refactor/convert the code to Java/C#?
    • What is your target infrastructure (AWS, Azure, Google Cloud, or on-premises private cloud)?
    • What specific database or transaction manager (e.g., CICS, DB2, IMS) do your applications rely on?

    ChatGPT SearchOct 15, 2026

    1. 1Rocket Software
    2. 2IBM Z
    3. 3AWS
    4. 4IBM GDPS
    5. 5Oracle
    6. 6Google Cloud Mainframe Modernization
    7. 7Rocket Enterprise Suite

    For legacy mainframe applications where high availability is the top priority, I would shortlist Rocket Software, IBM Z, and AWS-based modernization solutions. The best choice depends on whether you want to preserve your existing mainframe environment, emulate it on modern infrastructure, or gradually transform the applications.

    One important distinction: mainframe emulation preserves the existing application behavior, while modernization changes the platform or application architecture. Neither automatically guarantees high availability; you also need resilient data storage, failover, disaster recovery, and tested recovery procedures.

    My top recommendations

    • IBM Brings AI Power to Its Legendary Mainframes with New z17 Model - Washington News Brief

    1. IBM Z + GDPS

    (Best for maximum continuity)

    Best when keeping applications on the mainframe is acceptable.

    IBM Parallel Sysplex supports clustered workloads, workload balancing, and automated recovery. GDPS adds multisite disaster recovery and failover capabilities. IBM documents availability figures of up to 99.999999% for a specific, fully configured architecture; this is not a guarantee for every deployment.

    Choose it if: You run mission-critical CICS, IMS, or Db2 workloads and want to minimize migration risk.

    IBM Z resiliency ·

    • Modernize mainframe batch printing workloads on AWS by using Rocket Enterprise Server and LRS VPSX/MFI - AWS Prescriptive Guidance

    2. Rocket Software Enterprise Suite

    Best for emulation and replatforming.

    Rocket Enterprise Server enables COBOL and PL/I applications, along with supported mainframe transaction and batch workloads, to run on distributed infrastructure with relatively limited application changes. It is worth evaluating when moving away from the mainframe while preserving existing business logic.

    Choose it if: You want to run legacy applications on x86 servers or in the cloud rather than remain dependent on IBM Z hardware.

    Rocket mainframe modernization

    • Considerations for Moving to the Cloud

    3. Oracle Cloud Infrastructure (OCI)

    Best for cloud-hosted modernization with explicit HA/DR architecture.

    Oracle publishes a mainframe migration reference architecture that uses multiple fault domains, standby resources, load balancing, and Oracle Data Guard failover for database resilience. This is an architectural approach, not a turnkey emulator by itself.

    Choose it if: Your strategy is to replatform or refactor applications and design availability across cloud infrastructure.

    Oracle mainframe migration architecture

    • Dual Run by Google Cloud helps mitigate mainframe migration risks | Google Cloud Blog

    4. Google Cloud Mainframe Modernization

    Best for migration validation and incremental transformation.

    Google Cloud offers partner-based replatforming and Dual Run, which replays production traffic against modernized applications and compares results before cutover. Dual Run helps validate correctness; it is not itself a high-availability runtime.

    Choose it if: You want to reduce migration risk by comparing legacy and modernized application behavior before switching production over.

    Google Cloud mainframe modernization

    What I would implement for high availability

    Regardless of vendor, require these capabilities in the proposed solution:

    • Redundant application runtime: Multiple instances across independent failure domains, with load balancing and automated failover.
    • Resilient data: Synchronous or asynchronous replication appropriate to your recovery objectives, plus point-in-time recovery.
    • Defined RTO and RPO: Recovery Time Objective (how quickly service must return) and Recovery Point Objective (how much data loss is tolerable).
    • Legacy compatibility: Validate JCL, COBOL/PL/I, CICS or IMS transactions, batch schedules, database semantics, and external integrations.
    • Proven recovery: Conduct failover, site-loss, data-corruption, and rollback tests under production-like loads.

    For reference, AWS also publishes an architecture guide for operating modernized mainframe applications with high availability and disaster recovery. Read the AWS architecture guidance.

    My recommendation

    If your applications are business-critical and the primary goal is uptime, start by evaluating IBM Z with GDPS. If your strategic goal is to exit the mainframe while retaining legacy application behavior, evaluate Rocket Enterprise Suite alongside a cloud deployment architecture.

    One current procurement caveat: AWS's published documentation indicates that its former managed and self-managed Mainframe Modernization service experiences are no longer open to new customers. Confirm the availability of specific replacement offerings before making AWS the basis of a new implementation.

    Let me narrow this to the best fit

    1. What platform are you running today?

    IBM Z / z/OS

    Unisys mainframe

    Other or mixed mainframe environment

    Not sure

    2. What is your modernization goal?

    Keep applications largely unchanged

    Move applications off the mainframe

    Modernize incrementally while retaining the mainframe

    3. What availability target do you need?

    99.9% (about 8.8 hours downtime/year)

    99.99% or higher (about 53 minutes/year at 99.99%)

    Near-zero downtime, including site failures

    4. Where should it run?

    On-premises

    Hybrid cloud

    Public cloud

    Open to options

    [Compare solutions for my environment]

    Sources cited in this answer11

Also asked as

  • I'm looking for options to modernize or emulate our mainframe environment to improve high availability for our legacy applications.
  • We need to modernize or emulate our legacy mainframe applications and high availability is a must. What services are recommended for this?