Oracle 12c Multithreaded Multi Process

Oracle 12c: Multi Oracle 12c: Multi ProcessProcess Multi Multi ThreadedThreadedA A closercloser looklook atat thethe multimulti--processprocess multimulti--threadedthreaded model model forfor Oracle Oracle on Linux/Unixon Linux/Unix

Markus FlechtnerMarkus FlechtnerSenior ConsultantSenior Consultant

BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH

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Oracle 12c: Multi Process Multi Threaded2 11/4/2015

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About Markus Flechtner

Senior Consultant, Trivadis, Duesseldorf/Germany, since April 2008

Discipline Infrastructure Database @Trivadis

Working with Oracle since the 1990’s– Development (Forms, Reports, PL/SQL)

– Support

– Database Administration

Focus– Oracle Real Application Clusters

– Database Migration Projects

Teacher– O-RAC – Oracle Real Application Clusters

– O-NF12CDBA – Oracle 12c New Features for the DBA

Blog:http://markusdba.de/

@markusdba


Agenda

1. The problem & existing solutions

2. New in Oracle Database 12c: THREADED_EXECUTION

3. Architecture

4. Performance


5. Threaded Execution in the daily DBA business

6. Pros & Cons

The The problemproblem & & existingexisting solutionssolutions


The problem & existing solutions (1)

In the dedicated server achitecture on Unix/Linux:

– every client session has got its own server process

– these processes need memory and processor time

– there are many context switches

Many applications


Many applications

– Keep database sessions open and rarely execute SQL statements

Result

– Overhead on the database server

– Waste of system resources


Existing solutions

– Shared Server (Multithreaded Server)

– Database Resident Connection Pooling (DRCP)� not for all applications

– Universal Connection Pool (UCP)


– Connection Pools in general (Application Server)

All these solutions affect client sessions only


Overview on existing solutions


• From Oracle Database 12c Administrators Guide © Oracle Corporation


The “Multithreaded Oracle Process Model” does not replace these solutions but is a new method to reduce the resource consumption of a database instance on a Linux/Unix


these solutions but is a new method to reduce the resource consumption of a database instance on a Linux/Unix database server.

New in Oracle Database 12c: New in Oracle Database 12c: THREADED_EXECUTIONTHREADED_EXECUTION


""Multithreaded Oracle Process Model"Multithreaded Oracle Process Model"

Processes vs. Threads

Process

– A process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently

Process

Thread 1

Thread 2


Threads

– A thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler ..

Source: Wikipedia (http://en.wikipedia.org)

Thread 2

Multithreaded Oracle Process Model (1)

The “Multithreaded Oracle Process Model” on Unix/Linux enables the database instance to run instance processes as operating system threads

– Similar to Oracle on Windows

– No additional license costs; works on SE1, SE2, SE and EE

Configuration:


– Restart the instance

– Result: (most) background processes and local connections run as OS threads

ALTER SYSTEM SET threaded_execution=TRUE SCOPE=spfile SID='*'

Multithreaded Oracle Process Model (2)

For remote clients which connect via Oracle Net a parameter for the listener must be set in the listener.ora file:

– Restart the listener afterwards

DEDICATED_THROUGH_BROKER_<listener_name>=ON


If you want to run remote clients in threaded and non-threaded mode, a second listener is required

– Different port and/or host name resp. IP address

– DEDICATED_THROUGH_BROKER_<new_listener>=OFF (default)

Multithreaded Oracle Process Model (3) – DB Connect

Conn.Broker(Thread)

LISTENER

➊

➍

➋

➌Thread for


SGA

➍➎

➌Thread for

DB Session

ArchitectureArchitecture


Architecture (1) - Processes

Process list of an Oracle instance with THREADED_EXECUTION

oracle@te:~/ [TEST] ps –ef |grep $ORACLE_SID

oracle 6593 1 0 10:02 ? 00:00:00 ora_pmon_TEST

oracle 6595 1 0 10:02 ? 00:00:00 ora_psp0_TEST

oracle 6597 1 14 10:02 ? 00:00:03 ora_vktm_TEST

oracle 6601 1 23 10:02 ? 00:00:05 ora_u004_TEST

oracle 6607 1 99 10:02 ? 00:00:22 ora_u005_TEST


“Threaded Sessions” are “hidden” in the "ora_u<nnn>_<SID>“-processes

oracle 6607 1 99 10:02 ? 00:00:22 ora_u005_TEST

oracle 6613 1 0 10:02 ? 00:00:00 ora_dbw0_TEST

Architecture (2) - Processes

oracle@te:~/ [TEST] ps –ef |grep ora_u00

oracle 31220 1 2 21:18 ? 00:00:03 ora_u004_TEST

oracle 31226 1 11 21:18 ? 00:00:13 ora_u005_TEST

oracle@te:~/ [TEST] pidstat -t -p 31220

Linux 3.8.13-26.2.1.el6uek.x86_64 (te.markusflechtner.vm) 03/22/2014 _x86_64_ (4 CPU)

09:20:45 PM TGID TID %usr %system %guest %CPU CPU Command

09:20:45 PM 31220 - 0.01 0.01 0.00 0.02 3 ora_scmn_test

09:20:45 PM - 31220 0.00 0.00 0.00 0.00 3 |__ora_scmn_test

09:20:45 PM - 31221 0.00 0.00 0.00 0.00 1 |__oracle


09:20:45 PM - 31221 0.00 0.00 0.00 0.00 1 |__oracle

09:20:45 PM - 31222 0.00 0.00 0.00 0.00 0 |__ora_gen0_test

09:20:45 PM - 31223 0.00 0.00 0.00 0.00 2 |__ora_mman_test

09:20:45 PM - 31229 0.00 0.00 0.00 0.00 3 |__ora_dbrm_test

09:20:45 PM - 31233 0.00 0.00 0.00 0.00 1 |__ora_lgwr_test

09:20:45 PM - 31234 0.00 0.00 0.00 0.00 0 |__ora_ckpt_test

09:20:45 PM - 31235 0.00 0.00 0.00 0.00 3 |__ora_lg00_test

09:20:45 PM - 31236 0.00 0.00 0.00 0.00 3 |__ora_smon_test

09:20:45 PM - 31237 0.00 0.00 0.00 0.00 2 |__ora_lg01_test

09:20:45 PM - 31239 0.00 0.00 0.00 0.00 3 |__ora_lreg_test

Architecture (3) – V$PROCESS

SQL> select spid,stid,execution_type,pname from v$process

2 where spid is not null and (execution_type=‘PROCESS’ or pname in

3 ('PMON','SMON','DBW0','PSP0','VKTM','MMON','RECO','LGWR',’SCMN’));

SPID STID EXECUTION_ PNAME

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

6593 6593 PROCESS PMON

6595 6595 PROCESS PSP0

6597 6597 PROCESS VKTM


6597 6597 PROCESS VKTM

6601 6614 THREAD LGWR

6601 6601 THREAD SCMN

6601 6618 THREAD SMON

6607 6621 THREAD MMON

6607 6607 THREAD SCMN

6607 6619 THREAD RECO

6613 6613 PROCESS DBW0

Architecture (4)

The “SCMN”-Thread is the “thread listener” or “thread coordinator” within the process

The threaded sessions remain “dedicated server” sessions:

SQL> select p.execution_type,s.server,count(*)

2 from v$process p,v$session s

3 where s.paddr=p.addr

4 group by p.execution_type,s.server;


PGA is allocated from the shared pool (like with “Shared Server")

EXECUTION_ SERVER COUNT(*)

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

THREAD DEDICATED 38

PROCESS DEDICATED 4

Architecture (5)


Ora_uNNN processes are terminated after beeing idle for 30 seconds

Every threaded session needs a processes slot (=> Parameter PROCESSES) (� TNS-12602 “Connection pooling limit reached.”)

Architecture (6) – Memory Consumption

In average:18% less memoryconsumption with„THREADED_EXECUTION“


Architecture (7) – Connection Broker

Threaded Execution requires a Connection Broker

The new parameter CONNECTION_BROKERS is set automatically when THREADED_EXECUTION=TRUE

SQL> show parameter connection_brokers

NAME TYPE VALUE


NAME TYPE VALUE

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

connection_brokers string ((TYPE=DEDICATED)(BROKERS=1)),

((TYPE=EMON)(BROKERS=1))

Architecture (8) – Connection Broker & Listener

lsnrctl services

[..]

Service "TEST.markusflechtner.vm" has 1 instance(s).

Instance "TEST", status READY, has 2 handler(s) for this service...

Handler(s):

"N000" established:1 refused:0 state:ready

CMON <machine: te.markusflechtner.vm, pid: 1649_1668>


CMON <machine: te.markusflechtner.vm, pid: 1649_1668>

(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=34848))

"DEDICATED" established:0 refused:0 state:ready

LOCAL SERVER

[..]

Architecture (9) – Connection Broker & Listener

oracle@te:~/ [TEST] ps –ef |grep 1649

oracle 1649 1 9 19:24 ? 00:05:12 ora_u005_TEST

SQL> select spid,stid,pname,execution_type from v$process

2 where spid=1649 and stid=1668;

SPID STID PNAME EXECUTION_TYPE


SPID STID PNAME EXECUTION_TYPE

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

1649 1668 N000 THREAD

Architecture (10) - Miscellaneous

Threaded Execution & CPU usage

– No essential difference to "Non-Threaded-Execution"

Threaded Execution & Connect Time

– No essential difference to "Non-Threaded-Execution"

Threaded Execution on Windows


Threaded Execution on Windows

– The parameter has no effect

Multitenant Databases

– An OS process can contain sessions of multiple PDBs

PerformancePerformance


Performance (1) – Test Environment

Host

– Notebook Lenovo W510 / 32 GB RAM / SSD

– Oracle Linux 6.5

Virtual Server (VirtualBox)

– 16 GB RAM


– 16 GB RAM

Oracle Database

– Oracle 12.1.0.1

– 6000M SGA / 2000M PGA

– Non-CDB-Architecture

Performance (2) – Test with Swingbench

Test Software

– Swingbench 2.5.0.99 (www.dominicgiles.com)

– 3 tests with50 - 900 sessions, average of transactions


average of transactionsper second

Performance (3) - Results


Performance (4) – Other tests

Oracle presentation on „Real Application Testing":

– 5% better performance with THREADED_EXECUTION

Thomas Bordeau: http://blog.arkzoyd.com/2014/01/17/oracle-multithreaded-does-it-worth-a-try/

– Another test with Swingbench☺


Overall result:�Better performance�Better scalability

ThreadedThreaded ExecutionExecutionin in thethe dailydaily DBA DBA businessbusiness


OS Authentication (1)

OS authentication is not supported with threaded execution

– � ORA-1017 invalid username ..

– Password File required

– � Startup/Shutdown scripts have to be changed

Some Oracle tools require "Non-Threaded Execution"


Some Oracle tools require "Non-Threaded Execution"

– dbca

– dbua

– datapatch

OS Authentication (2) - Workaround

Store the password in a wallet

In short (see MOS-Note 340559.1 for details)

# create wallet

mkstore -wrl <wallet_location> -create

# add db authentication information

mkstore -wrl <wallet_location> -createCredential <db_connect_string>

<username> <password>


<username> <password>

# add the following lines to sqlnet.ora

WALLET_LOCATION =

(SOURCE =

(METHOD = FILE)

(METHOD_DATA = (DIRECTORY = <wallet_location_directory>)))

SQLNET.WALLET_OVERRIDE = TRUE

Connect to the DB using sqlplus sys/@<DB_Connect_String>

OS Authentication (3) – Other workarounds

sqlplus

/@"(ADDRESS=(PROTOCOL=BEQ)(PROGRAM=oracle)(ARGS='(ADDRESS=(PROTOCOL=BEQ))'

))" AS SYSDBA

# the way the clusterware agent connects to the instance

sqlplus


sqlplus

/@"(DESCRIPTION=(ADDRESS=(PROTOCOL=beq)(PROGRAM=/u00/app/oracle/product/12

.1.0.2/bin/oracle)(ARGV0=oracleGG03)(ENVS='ORACLE_HOME=/u00/app/oracle/pro

duct/12.1.0.2,ORACLE_SID=TEST,LD_LIBRARY_PATH=,ORACLE_BASE=')(ARGS='(DESCR

IPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))')(CONNECT_DATA=(SID=TEST))))"

AS SYSDBA

SQL Tracing

What‘s the name of the trace file?

� The filename contains SPID and STID

SQL> select spid,stid,execution_type,tracefile from v$process;

SPID STID E_TYPE TRACEFILE

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


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

NONE /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_ora_0.trc

6961 6961 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_pmon_6961.trc

6963 6963 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_psp0_6963.trc

6965 6965 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_vktm_6965.trc

6969 6971 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_gen0_6969_6971.trc

6969 6969 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_scmn_6969_6969.trc

6969 6972 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_mman_6969_6972.trc

6975 7000 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_ora_6975_7000.trc

..

How to kill database sessions?

As usual, sessions are identified via SID and SERIAL# in V$SESSION

Kill on database/instance level works fine:

But „kill -9 <spid>“ on OS level is not a good idea �

ALTER SYSTEM KILL SESSION ‘<sid>,<serial#>‘;


But „kill -9 <spid>“ on OS level is not a good idea

A thread cannot be killled from without the corresponding OS process

„kill -6 <stid>“ (SIGABRT) can help

– � find out the thread id via V$PROCESS or „pidstat“

– � execute „kill -6 <stid>“

Pros & Pros & ConsCons


Pros & Cons - Pro

Easy setup

Reduced memory consumption

Reduced number of processes on OS level

– � less context switches

Performance

Statements regarding performance and scalability have to be verified in each


Performance

– Equal or better than "non-threaded execution“

Scalability

– Equal or better than „non-threaded execution“

have to be verified in each individual case!

Test Threaded Execution with your application before you use it!

Pros & Cons - Con

Missing OS authentication

– Scripts have to be changed

„kill -9“ does not work

srvctl (RAC) does not work

– Unpublished bug


– Unpublished bug

Summary

There‘s not much information from Oracle on this feature

It is not really clear, why Oracle introduced this feature

There is no experience from customer projects so far, but if you accept the disadvantages(missing OS authentication, killing sessions on OS level), the „Multithreaded Multi Threaded“-model can make sense, if


Threaded“-model can make sense, if

– Your application does not support connection pools

– Your database is low on memory

But „Threaded execution“ cannot replace connection pools

Further InformationFurther Information


�MOS-Note 1639445.1: 12c: Threaded_execution=true Prevents OS Login As Sysdba�MOS-Note 1958348.1: Multi-Threaded Oracle Model�MOS-Note 340559.1: „Using The Secure External Password Store“�Oracle Presentation „Maximizing Database Performance Using Database Replay“�http://blog.arkzoyd.com/2014/01/17/oracle-multithreaded-does-it-worth-a-try/�http://dbwhisperer.wordpress.com/2013/10/04/multi-threaded-oracle-12c-Architektur-on-linux-2/

QuestionsQuestions andand AnswersAnswersMarkus FlechtnerMarkus FlechtnerSenior ConsultantSenior Consultant

Phone +49 211 5866 6470Phone +49 211 5866 [email protected]@Trivadis.com

@@markusdbamarkusdba http://markusdba.dehttp://markusdba.de

Download the slides from http://www.slideshare.net/markusdba

Please don‘t forget the session evaluation – Thank you!

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Oracle 12c Multithreaded Multi Process

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