What gets recorded
A decision log captures each significant decision as it is made: the question, the options considered, the choice, the reasoning and evidence behind it, who decided, who was consulted, the date, and any conditions or review triggers attached. It differs from meeting minutes in being organised around decisions rather than discussions.
Institutional memory as a decision asset
The log earns its keep in three moments. When a decision is challenged months later, the record distinguishes between "the reasoning was sound and the world changed" and "the reasoning was thin", which is the difference between learning and blame. When a settled question resurfaces, as settled questions do whenever a new executive arrives, the log ends the relitigation in minutes instead of meetings. And at review time, comparing recorded rationale against outcomes is the only honest way an organisation improves its judgement, because unrecorded reasoning gets rewritten by memory to match whatever happened.