Most of the world’s banking, insurance, and government transaction volume still runs on code written decades ago. The programmers who understand it are retiring, and the documentation that explains it is scattered across vendor manuals, forum threads, and institutional memory that leaves the building every time someone retires.
LegacyRunbook collects that knowledge in one place: status codes, abend codes, and error messages, sourced and organized so a developer or an IT decision-maker can actually find the answer they need, for the languages still running enterprise systems, not just COBOL.
We also connect teams facing a modernization decision with the vendors and consultancies who do that work, since figuring out who to call is often the harder problem.
Every number below is live — pulled from the same data the rest of the site runs on, not a stale figure written once and left to drift.
Reference database
466 entriesFile status, abend, message, exception, runtime, SQL, CICS, and database-error codes across 8 categories and all 8 languages. 278 are checked against an official vendor domain; the rest cite a real forum, blog, or community source and are labeled pending verification — see the methodology.
Browse the language hubs →Interactive tools
11 toolsCode lookup, error-message search, a job-log decoder, a COBOL copybook analyzer, a JCL annotator, compiler comparison, a modernization-timeline estimator, a skills-gap self-assessment, a migration checklist, and salary benchmarks. All client-side — nothing you type is sent anywhere.
See every tool →Vendor directory
26 vendorsConsultancies and platform vendors that actually do modernization work, categorized by approach (rewrite, wrapper, managed support, staffing) with a full writeup and sourced background per vendor, plus a 2-question quiz to narrow the list to your situation.
Browse vendors →Blog
24 postsOriginal reporting per language, not templated filler: history and market-position pieces, single-incident deep dives, myth-checking pieces, and technical investigations, each grounded in sources we actually fetched and checked.
Read the blog →FAQ
73 questionsDirect-answer entries phrased the way people actually search, marked up with FAQPage structured data so answer engines and AI assistants can cite them accurately.
See the language guide →Reading list
51 booksA curated, per-language list of real, findable books, each checked against a bookseller or publisher listing before inclusion, with an original note on who it's actually for.
Browse the reading list →