My Application Team getting below error and unable to initiate connection to the oracle database:
error: ORA-12516, TNS: listener could not find available handler with matching protocol stack
When I connected and checked on the database, (here my db is RAC server and using spfile)
On NODE 2:
Checking alert log file
vi alert_DEVD2.log
No errors found
$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Nov 18 19:35:36 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, Oracle Label Security,
OLAP, Data Mining, Oracle Database Vault and Real Application Testing options
SQL>
col name format a30
col value format a10
SQL> select name, value from v$spparameter where name in ('processes','sessions');
NAME VALUE
------------------------------ ----------
processes 400
sessions 400
or, check the max and current utilization of these parameters
select resource_name, current_utilization/limit_value*100,current_utilization, max_utilization,limit_value from v$resource_limit where resource_name in ('processes','sessions');
SQL> select count(*) from v$process;
COUNT(*)
----------
166
On NODE 1 :
SQL> select * from v$resource_limit where resource_name in ('processes','sessions');
ORA-00020: maximum number of processes (400) exceeded
ORA-20 errors will not be written to the alert log for
the next minute. Please look at trace files to see all
the ORA-20 errors.
SQL> select count(*) from v$process;
COUNT(*)
----------
380
SQL> select count(*) from gv$process;
COUNT(*)
----------
546
From the above output I see my processes are exceeded the value set by oracle(400) and resulting the error in alert log. Then checked the connections to the database:
Set linesize 280;
select count(*),INST_ID,username,osuser,status,machine from gv$session group by INST_ID,username,osuser,status,machine order by count(*),INST_ID;
Check the output from the above query and kill if find any INACTIVE sessions (idle)
Solution:
According to oracle, PROCESSES parameter specifies the maximum number of operating system user processes that can simultaneously connect to Oracle.
If the database is a RAC database then each NODE can have different values for PROCESS parameter.
SQL> sho parameter spfile;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string +DATADG/DEVD/spfiledevd.ora
Increase the Process parameter (replace xxx with any higher value)
SQL> alter system set processes=XXX scope=spfile;
System altered.
SQL> alter system set Sessions=XXX scope=spfile;
System altered.
*** Bounce the database to take effect ***
If processes=x
sessions=x*1.1+5
transactions=sessions*1.1
If the database is running on pfile then follow below steps:
1. Edit the database init.ora
2. Locate and increase the processes parameter to a higher value.
3. Save the init.ora file
4. Stop and restart the database
5. Re-connect to the database instance
For more Refer:
Troubleshooting Guide - ORA-20: Maximum Number Of Processes (%S) Exceeded (Doc ID 1287854.1)
