ORA-02020: too many database links in use

Cause:  The current session has exceeded the INIT.ORA open_links maximum.

Solution :-

SQL> show parameter open_links;

NAME                                 TYPE        VALUE

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

open_links                           integer              0

open_links_per_instance              integer     4

[oracle@ora ~]$ sqlplus sys/****@PDB as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Fri Oct 15 14:37:19 2021

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Last Successful login time: Fri Oct 15 2021 14:37:01 -04:00

Connected to:

Oracle Database 12c EE High Perf Release 12.2.0.1.0 - 64bit Production

SQL> shut immediate

Pluggable Database closed.

SQL> startup

Pluggable Database opened.

SQL> show parameter open_links;

NAME                                 TYPE        VALUE

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

open_links                           integer              4

open_links_per_instance              integer     4

SQL>