SQLException: ORA-02020: too many database links in use.

You can limit the number of connections from a user process to remote databases using the static initialization parameter OPEN_LINKS. This parameter controls the number of remote connections that a single user session can use concurrently in distributed transactions.

If you are not sure how many database links are opened up concurrently by your session's database application, you can query v$dblink

select in_transaction, count(*) from v$dblink group by in_transaction;

To Increase the Database Links limit.  Follow the below.

SQL> select name from v$database;

NAME
---------------------------
ORCL

SQL> show parameter open_links;

NAME                                 TYPE                                         value

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

open_links                           integer                                         4  

Default Value is > 4

Here have changed from 4 To 60.

SQL> ALTER SYSTEM SET OPEN_LINKS=60 SCOPE=SPFILE;

System altered.

NOTE: Parameter 'OPEN_LINKS' its static parameter. Hence database bounce is required, once change is made. Then only the new value will be effected.

SQL> select name from v$database;

NAME

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

ORCL

SQL> shut immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

Total System Global Area 1073741824 bytes

Fixed Size                  2101808 bytes

Variable Size             377490896 bytes

Database Buffers          687865856 bytes

Redo Buffers                6283264 bytes

Database mounted.

Database opened.

SQL> show parameter open_links;

NAME                                 TYPE                                         value

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

open_links                           integer                                         60

Thank You!