Functionality
This function module fills a table which was made known with theparameter OPEN_FILES. The file names of all archive filescurrently being processed with archiving function modules are filled inthe table.
DATA: BEGIN OF FILE_TABLE OCCURS 10,
FILENAME LIKE HEADA-DSN,
END OF FILE_TABLE.
...
CALL FUNCTION 'ARCHIVE_GET_OPEN_FILES'
TABLES
OPEN_FILES = FILE_TABLE.

Notes
A file which was opened for reading with the ABAP keyword OPENDATASET is not regarded as a second input file if it is openedagain, but the file is read from the beginning when it is nextaccessed.
This should never occur in archiving, otherwise the exceptionFILE_IO_ERROR would inevitably be raised.
The archiving function modules take this into account and initiate theexception FILE_ALREADY_OPEN if you try to open an archive filetwice.
If for a particular reason you do open archive files with OPENDATASET and work with the archiving function modules at the sametime, you must not open any files being accessed by the functionmodules.