ORACLE DB Connects only when I do not specify SID


I have an Oracle 19c database in a Unix server. SQLPLUS command connects only when I do not specify the SID.

sqlplus system/manager SQL*Plus: Release 19.0.0.0.0 - Production on Mon Jul 20 12:37:30 2020 Version 19.3.0.0.0  Copyright (c) 1982, 2019, Oracle.  All rights reserved.  Last Successful login time: Mon Jul 20 2020 11:45:41 +05:30  Connected to: Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production Version 19.3.0.0.0  SQL> 

However, when I try with the SID, it does not connect.

sqlplus system/manager@S19110  SQL*Plus: Release 19.0.0.0.0 - Production on Mon Jul 20 12:40:01 2020 Version 19.3.0.0.0  Copyright (c) 1982, 2019, Oracle.  All rights reserved.  ERROR: ORA-12537: TNS:connection closed   Enter user-name: 

I see the following in my listener.log :

TNS-12560: TNS:protocol adapter error TNS-00517: Lost contact Linux Error: 32: Broken pipe  

I googled the error and tried the following troubleshooting methods but no help.

  1. 6751 permission for $ ORACLE_HOME/bin/oracle
  2. Increase max number of processes in the database.

Please help.