How do I close log files that are open in OracleServiceORCL after inputting data into Oracle? I inserted data into a table called cell_local_stage1. With this procedure:
CREATE TABLE cell_local_stage1
    (
      construct_id NUMBER(10),
      n_term VARCHAR2 (50),
      enz_name VARCHAR2 (50),
      c_term VARCHAR2 (50),
      cpp VARCHAR2 (50),
      mutations VARCHAR2 (50),
      g_batch VARCHAR2 (50),
      p_batch VARCHAR2 (50),
      c_batch VARCHAR2 (50),
      
      emptycol VARCHAR2(50),
      ind_var_number NUMBER,
      study_id VARCHAR2 (50),
      char_id NUMBER,
      concentration NUMBER (6, 2),
      valid NUMBER (1) DEFAULT 1,
      endpoint1 NUMBER (1),
      method1 VARCHAR2 (50),
      methodv1 VARCHAR2 (50))
      
      
    ORGANIZATION EXTERNAL (
    TYPE ORACLE_LOADER
    DEFAULT DIRECTORY data_to_input
    ACCESS PARAMETERS (
        RECORDS DELIMITED BY NEWLINE 
        SKIP 1
        BADFILE bad_files:'badflie_insert_into_cell_local_stage1_from_cell_local.bad'
        FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '&quot;'
        MISSING FIELD VALUES ARE NULL 
        ) 
    LOCATION ('CELL_LOCAL.CSV')
    ) REJECT LIMIT UNLIMITED;

I got a log file that has this information:

 LOG file opened at 08/17/20 22:00:47

Total Number of Files=1

Data File: CELL_LOCAL.CSV

Log File: CELL_LOCAL_STAGE1_4908_22980.log

And when I try to delete that file this messages says that the file is still open:

I was able to delete the CSV files, but not the log files. I didn't know I could even open these log files in Oracle.
Sorry for such a basic question.
Well, its Oracle on Windows, such issues are not uncommon there.
Similar, but not exactly your issue:
Bug 30191227 - HANDLE LEAK ON EXTERNAL TABLE LOG FILE IN WINDOWS PLATFORM
No fix exists yet for it, not even in 19c. Suggested workaround:
WORKAROUND:
-----------
Manually release the file handle using Windows process explorer.

Of course database restart works as well (Oracle on Windows runs as a single process).
Process Explorer