DSXchange

want to delete datasets over 3 months using orchadmin

what would be the command ?

Basically it is "orchadmin delete" but I'm guessing this is more about the three months part. If you mean three months since it was created or modified, you can use find for that and then send them to orchadmin one by one.

Or even use the -exec option in find to execute the orchadmin rm {} command.

Exactly. That or xargs are the two options of choice with find.