Log Times:
ORA-12516：TNS:listener could not find available handler with matching protocol stack
Solution:
1. Switch to the oracle user:
su - oracle
2. Stop the database listener:
lsnrctl stop
3. Once connections down, landing database:
sqlplus / as sysdba
4. Modify the processes and sessions parameters:
1) View processes and sessions parameters
SQL> show parameter processes;
SQL>show parameter sessions ;
2) modifying processes and sessions parameter
SQL> alter system set processes=300 scope=spfile;
SQL>alter system set sessions=335 scope=spfile ;
SQL>commit ;
3) Restart the database
Oracle server restart to take effect
4) instructions
ORACLE number of connections the number of processes (Sessions) and its parameter file (process) relating to their relationship: sessions = (1.1 * process + 5)
5) related queries
. A number of connections to the database query the current process: select count (*) from v $ process;
. b check the database connections for the current session: Elect COUNT (*) from v $ the session;
. c See concurrent connections to the database: SELECT COUNT (*) from the session $ WHERE V Status = 'the ACTIVE';
. d view the current session of the establishment of the database: the SELECT sid, Serial #, username, Program, Machine, v $ Status from the session;
. e the maximum number of connections allowed by the database query: SELECT WHERE value from V $ Parameter name = 'Processes'; or: show parameter processes;
. f The maximum number of connections allowed to modify a database: ALTER System Processes SET = 300 = SPFILE scope;
. G view which users are currently using the data:
select osuser,a.username,cpu_time/executions/1000000||'s',sql_fulltext,machine
from v$session a,v$sqlarea b
where a.sql_address = b.address
order by cpu_time/executions desc;