When you use -daos on|off on a mail directory, compaction will be executed on all the databases located on directory.
When you use "-daos on" switch, DAOS will be enabled for non-enabled databases and copy-style compaction will be performed on already enabled databases.
if there are more number of files on the directory, this process takes more time(complete day)
So when using "-daos on" option, compact task should skip the databases for which DAOS is already enabled based on "on|off" option provided in the command.
In this way the time taken by the compact task can be reduced and saves system resources.