Oracle Solution for Error ora-01668

ORA-01668: standby database requires DROP option for offline of data file

What triggered the Error:

Attempting to take a datafile offline in a standby database without specifying the DROP option. Files that are offline in a standby database are not recovered, and are likely to be unusable if the standby is activated. Note that specifying DROP does not prevent bringing the file online later.

What should we do to fix it:

Specify the DROP option or leave the file online.