What to Do When Legacy Software Has No Documentation

First response

1. Image or back up the machine, application and databases.
2. Interview operators and capture critical workflows and exceptions.
3. Inventory files, dependencies, configuration and startup.
4. Observe inputs, outputs and database/file changes.
5. Identify network, printer, serial and hardware integrations.
6. Rank functions by business impact and recovery urgency.

Create the first useful documentation

Produce a one-page architecture, dependency list, configuration locations, backup/recovery steps and known failure points. Document what is observed versus assumed before making code or platform changes.

Use the archaeology checklist, configuration recovery, system documentation and the pillar.