Document the operating architecture
- Executables, services and startup sequence
- Runtime, DLL/COM, driver and license dependencies
- Databases, files, shares and backup/restore
- Network, serial, hardware and protocol integrations
- Configuration, scheduled jobs and manual procedures
- Deployment steps and known failure modes
Keep it verifiable
Attach sources such as paths, version output, traces, screenshots or tested recovery steps. Record owner, date and confidence; use diagrams only where they clarify a dependency or sequence. Validate documentation by having another operator restore or execute a bounded workflow.
Use dependency mapping, configuration recovery, undocumented-software analysis and the pillar.