How to Copy Files in ASM

cp command in ASMCMD actually not copies system generated the file but creates an alias for real file. Here is a procedure to copy system generated file (redo log) from one asm datagroup to an other:

1-) Login a database which has access to asm disk groups

2-) Create following directories

CREATE OR REPLACE DIRECTORY SOURCE_DIR AS '+DG1/DBNAME/ONLINELOG';
CREATE OR REPLACE DIRECTORY DEST_DIR AS '/..filesystem_path../ONLINELOG';

3-) Copy asm file to filesystem

BEGIN
  dbms_file_transfer.copy_file(source_directory_object =>
  'SOURCE_DIR', source_file_name => 'filename',
  destination_directory_object => 'DEST_DIR',
  destination_file_name => 'filename');
END;
/

4-) Copy file on filesystem back to asm

CREATE OR REPLACE DIRECTORY SOURCE_DIR AS '/..filesystem_path../ONLINELOG';
CREATE OR REPLACE DIRECTORY DEST_DIR AS '+DG2/DBNAME/ONLINELOG';
BEGIN
  dbms_file_transfer.copy_file(source_directory_object =>
  'SOURCE_DIR', source_file_name => 'filename',
  destination_directory_object => 'DEST_DIR',
  destination_file_name => 'new_filename');
END;
/