FLUSHALL
Syntax
FLUSHALL [ASYNC | SYNC]
Time complexity: O(N) where N is the total number of keys in all databases
ACL categories: @keyspace, @write, @slow, @dangerous
Delete all the keys of all the existing databases, not just the currently selected one. This command never fails.
FLUSHALL will always asynchronously flush databases. Specifying ASYNC or SYNC does not currently affect the behavior.
Note: an asynchronous FLUSHALL command only deletes keys that were present at the time the command was invoked. Keys created during an asynchronous flush will be unaffected.