Knowing how things are set up.
WHAT TO DOCUMENT
What systems exist How they are configured How they connect What depends on what Who owns each
WHY DEPENDENCIES MATTER MOST
Because they determine what an outage affects, and what a change risks.
WHAT A CONFIGURATION RECORD SHOULD CONTAIN
Identification Location Configuration details Relationships to other items Change history
WHAT MAKES DOCUMENTATION FAIL
Being out of date.
WHY
Out-of-date documentation is worse than none, because it is trusted.
WHAT PREVENTS THAT
Updating at the time of the change, as part of the change process.
WHY AT THE TIME
Documentation updated later is not updated.
WHAT TO KEEP SEPARATELY
Anything needed when systems are unavailable.
WHERE
Printed, or somewhere independent.
WHAT TO VERIFY PERIODICALLY
Records against reality.
WHAT YOU WILL FIND
Systems not recorded, and records for systems removed.
