How to Kill Zombie Processes on Linux

###How to Kill Zombie Processes on Linux

 Defunct processes may also be known as "zombie" processes. They do not use any system resources - CPU, memory etc. but may be seen as entries in their respective operating system process table. 

 A zombie is already dead, so you cannot kill it. To clean up a zombie, it must be waited on by its parent, so killing the parent should work to eliminate the zombie. (After the parent dies, the zombie will be inherited by pid 1, which will wait on it and clear its entry in the process table.) If your daemon is spawning children that become zombies, you have a bug. Your daemon should notice when its children die and wait on them to determine their exit status. 

 ##What Causes Zombie Processes on Linux?

 A poorly written parent process might not call the wait() function when the child process is created. This means nothing is watching for state changes in the child process, and the SIGCHLD signal will be ignored. Or, perhaps another application is affecting the execution of the parent process, either due to poor programming or malicious intent.

 [oracle@oracle ~]$ ps -ef|grep zombie 

oracle 175489580 0 11:33 pts/0 00:00:00 grep --color=auto zombie

ORA-00020: No more process state objects available

 How to increase processes, sessions, and transactions parameters in Oracle 12R1.

Whenever DB processes are utilized 100% then it’s NOT allowed any new sessions/connections to DB’s instances and we get the below error:

ORA-00020: No more process state objects available

ORA-20 errors will not be written to the alert log for

If we are planning to increase “PROCESSES” parameter so, we  should also plan to increase the “SESSIONS” and “TRANSACTIONS” parameters. 

A basic formula for determining  these parameter values is as follows:

 

        processes=x

        sessions=x*1.1+5

        transactions=sessions*1.1

Cause: All process state objects are in use.

Action: Increase the value of the PROCESSES initialization parameter.

Before starting on the solution, we understand what is processes, sessions & transactions:

PROCESSES: It specifies the maximum number of operating system user processes that can simultaneously connect to Oracle. Its value should allow for all background processes such as locks, 

job queue processes, and parallel execution processes.

The default values of the SESSIONS and TRANSACTIONS parameters are derived from the PROCESSES parameter. Therefore, if we change the value of PROCESSES, 

We should evaluate whether to adjust the values of those derived parameters.

SESSIONS: It specifies the maximum number of sessions that can be created in the system. Because every login requires a session, this parameter effectively determines the maximum number of concurrent users in the system. 

We should always set this parameter explicitly to a value equivalent to our estimate of the maximum number of concurrent users, plus the number of background processes, plus approximately 10% for recursive sessions. Oracle uses the default value of this parameter as its minimum. Values between 1 and the default do not trigger errors, but Oracle ignores them and uses the default instead.

TRANSACTIONS: It specifies the maximum number of concurrent transactions. Greater values increase the size of the SGA and can increase the number of rollback segments allocated. 

The default value is greater than SESSIONS (and, in turn, PROCESSES) to allow for recursive transactions.

Solution:-

[oradb@oracle ~]$ sqlplus / as sysdba

SQL> show parameter processes

NAME                                 TYPE        VALUE

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

aq_tm_processes                      integer     1

db_writer_processes                  integer     1

gcs_server_processes                 integer     0

global_txn_processes                 integer     1

job_queue_processes                  integer     2

log_archive_max_processes            integer     4

processes                            integer     400

SQL> show parameter sessions

NAME                                 TYPE        VALUE

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

java_max_sessionspace_size           integer     0

java_soft_sessionspace_limit         integer     0

license_max_sessions                 integer     0

license_sessions_warning             integer     0

sessions                             integer     800

shared_server_sessions               integer

SQL> show parameter transactions

NAME                                 TYPE        VALUE

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

transactions                         integer     880

transactions_per_rollback_segment    integer     5

SQL>

If we are planning to increase “PROCESSES” parameter so, we  should also plan to increase the “SESSIONS” and “TRANSACTIONS” parameters. A basic formula for determining  these parameter values is as follows:

          processes=x

        sessions=x*1.1+5

        transactions=sessions*1.1

Before altering parameters we need to take a backup of pfile.

SQL> create pfile from spfile;

SQL> alter system set processes=500 scope=spfile;

SQL> alter system set sessions=555 scope=spfile;

SQL> alter system set transactions=610 scope=spfile;

After resetting the parameters we need to bounce the database-

SQL>shutdown immediate;

SQL>startup;

After that will check the settings of parameters-

SQL> show parameter processes;

SQL> show parameter session;

SQL> show parameter transactions;

ORA-39087: directory name DPUMP_DIR is invalid

 This error may be returned if you are trying to export or import using oracle data pump, 

but invalid directory name has been provided during this process. 

Following is an example of this.

Error:

[oracle@hostname ~]$ expdp system/manager DIRECTORY=dpump_dir DUMPFILE=system.dmp logfile=system.log schemas=system

Export: Release 11.2.0.3.0 - Production on Wed Aug 2022 10:07:55 

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

With the Partitioning, Automatic Storage Management, OLAP, Data Mining and Real Application Testing options

ORA-39002: invalid operation

ORA-39070: Unable to open the log file.

ORA-39087: directory name DPUMP_DIR is invalid

Solution:

Check the directory is exists or not, If not exist then create the directory with proper path: 

If the directory exists then check grant on the directory, if the grant missing then provide grant 

SQL> CREATE OR REPLACE DIRECTORY DPUMP_DIR AS '/u01/dpump'

NOTE :

If SYS or SYSTEM user will be used for export/import, granting rights on above directory are not needed, 

otherwise grant rights to the user performing export/import

SQL> GRANT READ, WRITE ON DIRECTORY DPUMP_DIR TO SYSTEM;

Now try to take export again. It should work.