MAXDATAFILES db_files open files

select value from v$parameter where name = 'db_files'; <<<<<<

select records_total from v$controlfile_record_section where type = 'DATAFILE'; <<<<<<<<<< MAXDATAFILES

The default values for MAXDATAFILES is 30, the maximum value can be increased is 65534 (recreating the control file).

Note that within this there is a restriction of 1022 files per tablespace that cannot be changed.

If you decide to increase the limit of the number of files you should check also at OS level the maximum number of open files

Here you have the recommended values:

Resource Shell Limit   Resource    Soft Limit     Hard Limit

--------------------   --------    ----------     ----------

Open file descriptors  nofile      at least 1024  at least 65536