What happens when you use a tool
- Opening a page downloads the tool's code once, like any web page. From then on, everything you paste or open is processed by that code inside your browser.
- There is no server behind the tools, no database and no account. There is nothing on our side that could receive your copybook, file or JCL.
- The tools are rule-based engines, not AI. The same input always gives the same answer, and every rule they follow comes from IBM's documentation.
Why your data cannot leave your device
- Every page carries a security policy that forbids it from making network requests (
connect-src 'none') or submitting forms. The browser itself enforces this, so even a programming mistake cannot send data out. - No cookies, no analytics script, no advertising and no third-party code. Visitor totals come only from the hosting service's own counts.
- Before every release an automated test types a marker into every tool and fails the release if any request leaves the page.
How accuracy is checked
- Each rule is checked against IBM documentation, and the source is recorded. Every error-code page links to the IBM pages it was checked against.
- Each tool has known-answer tests: inputs with results worked out by hand, checked on every release.
- New engines and new code explanations get an independent review before they go live.
Accuracy, tool by tool
Every tool page shows one of three notes:
- Checked against IBM rules: the tool applies documented rules exactly, within the limits stated on its page.
- Simulation, confirm on z/OS: the tool imitates what z/OS would do (the COBOL debugger, the DFSORT sample run). It follows the documented rules, but the real system has the final word.
- Site search, no AI: search only finds this site's own pages; it never writes an answer of its own.
| Tool | Accuracy | Limits |
|---|---|---|
| Copybook viewer | Checked against IBM rules | Sizes follow Enterprise COBOL storage rules (PIC, COMP, COMP-3, OCCURS, REDEFINES) and are covered by known-answer tests. SYNC slack bytes are an estimate (confirm with the compiler MAP listing), and compiler options such as TRUNC are not modelled. |
| Record decoder | Checked against IBM rules | Decoding follows the copybook and the code page you choose; packed, binary and zoned rules are covered by known-answer tests. The tool cannot detect the code page, so pick the one the file was written in. |
| Packed decimal calculator | Checked against IBM rules | Follows the z/Architecture packed and zoned decimal formats, including the sign half-byte; covered by known-answer tests. |
| EBCDIC converter | Checked against IBM rules | Uses the standard IBM code page tables for 037, 500, 273, 285, 1140, 1148 and 1047. |
| Mainframe date converter | Checked against IBM rules | Follows the TIME macro, Language Environment (Lilian) and TOD clock definitions; covered by tests. STCK values are shown in UTC. |
| Block size and space calculator | Checked against IBM rules | Uses the 3390 track-capacity formula for blocks without keys. Other device types and compressed or extended-format data sets are not covered. |
| JCL checker | Checked against IBM rules | Checks the common rules from the z/OS JCL Reference (columns, continuations, DISP, SPACE, DCB, names). It is not a full JCL converter: symbols, procedures and system defaults are only resolved by z/OS itself. |
| JCL generator | Checked against IBM rules | Templates follow the z/OS JCL and utility references. Replace the example names and check your site's JOB card, classes and storage rules before you submit. |
| DFSORT helper | Simulation, confirm on z/OS | Statements follow the DFSORT reference. The sample run simulates the common statements on your own sample records; it is not DFSORT itself, so check the real output. |
| COBOL debugger | Simulation, confirm on z/OS | A simulation that follows Enterprise COBOL rules, checked by two independent reviews and tests. Results can depend on compiler options, and Db2 and CICS results are the ones you type in. Confirm on z/OS. |
| Site search | Site search, no AI | A search of this site's own pages. It is not an AI and does not invent answers. |
Before you change anything in production
The tools help you understand and prepare. Always confirm against IBM documentation and your own system before changing production data, programs or settings.
Found a mistake?
Please tell us: [email protected]. Wrong answers are fixed first, before any new feature.