View the number of Oracle connections

1. view the maximum number of Oracle connections
SQL> show parameter processes # maximum number of connections

2. Modify the maximum number of connections
SQL> alter system set processes = value scope = spfile # value indicates the number of connections to be set.

After the database is restarted, you can see that the modified maximum connection has taken effect.

3. view the current number of connections
SQL> select * from V $ SESSION where username is not null # view current connections

4. view the number of connections of different users
SQL> select username, count (username) from V $ SESSION where username is not null group by username

5. View concurrent connections
SQL> select count (*) from V $ SESSION where status = 'active' # view concurrent connections

6. Check the number of connections of a specified program.
SQL> select count (*) from V $ SESSION where program = 'jdbc Thin client' # Number of JDBC connections to Oracle