DBA documentation for cover scenarios

Specific to the role of a DBA, for your typical working 'day to day' administration activities, plus any project/development work you are assigned responsibility for, are there any generally accepted essential items you could/should include in terms of documentation, whereby if you were unavailable for a few weeks and a deputy had to stand in take on your daily workload, what kind of things would they typically need to give them a fighting chance of being able to do so?
Does you company/manager mandate that you maintain certain documentation of your daily admin work/ongoing project or development work in a specific location - if so what does that include?
We are trying to identify some standards/'bare essentials' to minimise the risk if key staff are unavailable for short/long term, and seeing what kind of documentation you keep to help with this, in a specific role such as DBA, would be most useful. DBA has been identified as a crtiical role in the IT section.