Compare approaches
PYD ENTERPRISES vs. lift-and-shift rehosting
Rehosting recompiles or emulates mainframe workloads on x86 servers or cloud infrastructure with minimal code change. It cuts platform cost without touching the business logic. PYD ENTERPRISES documents that logic so it can be changed later, which is why the two are often complementary.
THE SHORT VERSION
Rehosting changes where the code runs; it does not change what you know about it. Do it for platform cost, and extract the specification if you will ever need to change the rules.
Side by side
Lift-and-shift rehosting vs. PYD ENTERPRISES
| Dimension | Lift-and-shift rehosting | PYD ENTERPRISES |
|---|---|---|
| Goal | Lower platform and MIPS cost quickly | Understand and specify business behavior |
| Code changes | Minimal: recompile, adjust JCL and data access | None: PYD ENTERPRISES reads code, it does not change it |
| Business logic | Unchanged and still undocumented | Extracted to DMN, OpenAPI and JSON Schema |
| Skills problem | Still need COBOL, CICS and JCL skills on the new platform | Gives non-COBOL engineers a readable specification |
| Time to value | Months for infrastructure savings | Weeks for the specification |
| Fits together? | Yes: rehost first, specify for later re-architecture | Yes: scan before or after rehosting; same source either way |
What rehosting does
Rehosting platforms provide COBOL compilers, CICS-compatible transaction monitors, JCL execution and VSAM emulation on Linux or Windows, on premises or in a public cloud. The application code changes little: programs are recompiled, JCL is adjusted, VSAM files are migrated to the emulated store or a relational database behind a compatibility layer. The payoff is infrastructure cost, often the most visible line item in a mainframe budget.
What it leaves in place
After a rehost, the business logic is exactly as it was: same programs, same copybooks, same paragraph structure, same knowledge concentrated in a shrinking group of people. US federal agencies offer a public view of the long-term cost of that position: GAO-16-468 found that about 75% of the federal FY2015 IT budget went to operating and maintaining existing systems. Rehosting can lower the run cost; it does not by itself make the system easier to change.
That matters when the business needs a new product, a regulatory change lands, or the program later decides to re-architect. At that point someone still has to work out what the code does.
Using both
Because PYD ENTERPRISES reads source rather than runtime, it works the same before and after a rehost. Some programs scan first, so the rehost team knows which programs are dead and need not be migrated at all. Others rehost first for cost and run PYD ENTERPRISES when they start breaking the application into services, using the DMN tables and OpenAPI contracts as the design input and the generated fixtures as the equivalence check against the rehosted system.
Fair is fair
When lift-and-shift rehosting is the right call.
We would rather lose a deal than sell PYD ENTERPRISES where it does not fit.
- The main driver is platform cost or an expiring hardware or software contract, and the business logic does not need to change soon.
- The application is stable and well supported by its current team, and the goal is only to move it.
- You need a short-term exit with low change risk and plan to re-architect later.
- Data residency or latency pushes you to a specific infrastructure that still needs to run COBOL workloads.
FAQ
Common questions.
Does PYD ENTERPRISES support rehosted COBOL dialects?
PYD ENTERPRISES parses IBM Enterprise COBOL and Micro Focus COBOL, which covers most rehosted estates. Vendor-specific extensions can be added as dialect packs.
Should we scan before or after rehosting?
Before, if you want to avoid migrating dead code. After, if the rehost is already scheduled. The output is the same because the source is the same.
Does rehosting make extraction unnecessary?
No. It changes the platform, not the documentation. If anyone will need to change the rules later, the specification is still the missing piece.
Other comparisons
- PYD ENTERPRISES vs. manual code auditUse people for judgment and tools for enumeration.
- PYD ENTERPRISES vs. generic llm migrationUse language models to describe rules, not to find them.
- PYD ENTERPRISES vs. automated transpilersTranspilation moves the code; specification extraction moves the knowledge.
- PYD ENTERPRISES vs. rewrite from scratchRewrite the system, not the knowledge.
Compare on your own code.
Run PYD ENTERPRISES on up to 100,000 lines for 14 days in your VPC and put the output next to whatever you use today.