do RMAN erase all archivelogs in mode archivelog multiplexing ?

[ebrian]

You could perform the delete as follows:

DELETE NOPROMPT ARCHIVELOG LIKE '<first_archivelog_location>%' 
    BACKED UP 1 TIMES TO DEVICE TYPE DISK;

however, you will still need to consider how you are going to manage the removal of the archivelogs in the second location and let RMAN know when these are removed.