Oracle 10g Rac Load Balance Connection

8/14/2019 Oracle 10g Rac Load Balance Connection

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Oracle 10g RAC load-balancing configuration

This is a discussion on Oracle 10g RAC load-balancing configuration within the Database

Discussions forums in Database and Unix Discussions category; Hi, I am new to RACadministration. I have been trying to configure load-balancing across two nodes in a cluster.

192.168.2.5, 192.168.2.6 are public IP addresses of the nodes and 192.168.2.9, 192.168.2.10are the VIP addresses. My configuration files look like this:

-------------------- SQLNET.ORA ---------------------------

TRACE_LEVEL_CLIENT = OFFnames.directory_path = (TNSNAMES)

names.default_domain = worldname.default_zone = world

break_poll_skip=2000000000----------------------------------------------------------------------------

--------------------- TNSNAMES.ORA --------------------------

TPCC.world =

(DESCRIPTION =(load_balance = on)

(failover = on)(ADDRESS_LIST =

(FAILOVER = ON)(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.9)(PORT = 1521))

(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.10)(PORT = 1521)))

(CONNECT_DATA =

(SERVICE_NAME = tpcc))

)

TPCC1.world =(DESCRIPTION =

(load_balance = on)(failover = on)

(ADDRESS_LIST =(FAILOVER = ON)


(CONNECT_DATA =(SERVICE_NAME = tpcc)

)

)

TPCC2.world =(DESCRIPTION =


(ADDRESS_LIST =(FAILOVER = ON)


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))

EXTPROC_CONNECTION_DATA =(DESCRIPTION =

(ADDRESS_LIST =(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))

(CONNECT_DATA =

(SID=PLSExtProc)(PRESENTATION=RO)))

LISTENERS_TPCC =

(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.9)(PORT = 1521))


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

--------------------- LISTENER.ORA --------------------------LISTENER_TPCC1 =

(DESCRIPTION =(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.9)(PORT = 1521))(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.5)(PORT = 1521))

)(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))))

LISTENER_TPCC2 =

(DESCRIPTION =

(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.10)(PORT = 1521))


(ADDRESS_LIST =(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))

)

)

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

INIT.ORA ---------------------------

BACKGROUND_DUMP_DEST =/home/oracle/app/oracle/OraHome_1/rdbms/log

USER_DUMP_DEST =/home/oracle/app/oracle/OraHome_1/rdbms/log

control_files = ?/dbs/tpcc_disks/control_001


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parallel_max_servers = 48DB_BLOCK_SIZE = 2048

recovery_parallelism = 20compatible = 10.1.0.2

db_name = tpccdb_files = 200

db_file_multiblock_read_count = 16pga_aggregate_target = 800m

dml_locks = 500log_checkpoint_interval = 100000000

log_checkpoints_to_alert = TRUEopen_cursors = 400

processes = 200

sessions = 600transactions = 400

transactions_per_rollback_segment = 1

cursor_sharing = forcecursor_space_for_time = TRUE

timed_statistics = TRUEdisk_asynch_io = TRUE

db_writer_processes = 5hpux_sched_noage = 178

db_cache_size = 2700m

java_pool_size = 0large_pool_size = 300m

shared_pool_size = 1000m

log_buffer = 1024000db_recycle_cache_size = 16m

db_cache_advice = ON

plsql_optimize_level = 2undo_management = AUTO

#####cluster parameter #######################cluster_database = true

cluster_database_instances = 2tpcc1.thread = 1

tpcc1.instance_name = tpcc1

tpcc1.instance_number = 1tpcc1.undo_tablespace = UNDOTBS1

tpcc2.thread = 2

tpcc2.instance_name = tpcc2tpcc2.instance_number = 2

tpcc2.undo_tablespace = UNDOTBS2tpcc1.local_listener = 'LISTENER_TPCC1'

tpcc2.local_listener = 'LISTENER_TPCC2'remote_listener = 'LISTENERS_TPCC'

#############################################

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


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On both the nodes I have started the listeners LISTENER_TPCC1 andLISTENER_TPCC2 respectively and their status looks similar to this:

-------------------------------------------------------------------> lsnrctl start LISTENER_TPCC1

LSNRCTL for HPUX: Version 10.1.0.2.0 - Production on 25-APR-2006

20:16:12

Copyright (c) 1991, 2004, Oracle. All rights reserved.

Starting /home/oracle/app/oracle/OraHome_1/bin/tnslsnr: please wait...

TNSLSNR for HPUX: Version 10.1.0.2.0 - Production

System parameter file is

/home/oracle/app/oracle/OraHome_1/bench/bench1000/benchrun/network/listener.ora

Log messages written to/home/oracle/app/oracle/OraHome_1/network/log/listener_tpcc1.log

Listening on:(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168. 2.9)(PORT=1521)))

Listening on:(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168. 2.5)(PORT=1521)))

Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC)) )

Connecting to(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.

2.9)(PORT=1521)))STATUS of the LISTENER

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

Alias LISTENER_TPCC1Version TNSLSNR for HPUX: Version 10.1.0.2.0 -Production

Start Date 25-APR-2006 20:16:12Uptime 0 days 0 hr. 0 min. 0 sec

Trace Level offSecurity ON: Local OS Authentication

SNMP OFF

Listener Parameter File/home/oracle/app/oracle/OraHome_1/bench/bench1000/benchrun/network/listener

.ora

Listener Log File/home/oracle/app/oracle/OraHome_1/network/log/listener_tpcc1.log

Listening Endpoints Summary...(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168. 2.9)(PORT=1521)))

(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168. 2.5)(PORT=1521)))(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC)) )

The listener supports no servicesThe command completed successfully

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


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Everytime I try to start the database instances I get the following

error:

SQL> startup pfile=init.oraORA-00119: invalid specification for system parameter REMOTE_LISTENER

ORA-00132: syntax error or unresolved network name 'LISTENERS_TPCC'ORA-01078: failure in processing system parameters

Can somebody please help me out in pointing out what am I doing wrong?

Thanks a lot,

Sudhanshu

SOLUTION

Thanks for your time guys. I tried quite a few things in the pfile -

single quotes, without quotes, double quotes - finally I just took theentry from the tnsnames.ora and pasted it there in the pfile itself. So

the entries in the new pfile look like this:

tpcc1.local_listener = '(ADDRESS =

(PROTOCOL=TCP)(HOST=192.168.2.9)(PORT=1521))'tpcc2.local_listener = '(ADDRESS =

(PROTOCOL=TCP)(HOST=192.168.2.10)(PORT=1521))'

remote_listener = '(ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST =192.168.2.9) (PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST =

192.168.2.10)(PORT = 1521)))'

After this the database came up without problems. Still connection loadbalancing was not working. So I figured it had to do something with

tnsnames.ora. I rewrote the tnsnames.ora file as:

TPCC.WORLD =(DESCRIPTION =


(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.9)(PORT = 1521))


(CONNECT_DATA = (SERVICE_NAME = tpcc))

)

TPCC1.WORLD =

(DESCRIPTION =(load_balance = on)

(failover = on)


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(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.9)(PORT = 1521))(CONNECT_DATA =

(SERVICE_NAME = tpcc)(INSTANCENAME = tpcc1)

(SERVER = DEDICATED))

)

TPCC2.WORLD =(DESCRIPTION =


(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.2.10)(PORT = 1521))


(INSTANCENAME = tpcc2)

(SERVER = DEDICATED))

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

Restarting the listeners the new status was like this:

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

--------------------------> lsnrctl services LISTENER_TPCC1

LSNRCTL for HPUX: Version 10.1.0.2.0 - Production on 27-APR-2006

11:54:26

Copyright (c) 1991, 2004, Oracle. All rights reserved.

Connecting to (DESCRIPTION=(address=(protocol=ipc)(key=extproc)) )Services Summary...

Service "plsextproc" has 1 instance(s).Instance "plsextproc", status UNKNOWN, has 1 handler(s) for this

service...Handler(s):

"DEDICATED" established:0 refused:0

LOCAL SERVERService "tpcc" has 2 instance(s).

Instance "tpcc1", status READY, has 2 handler(s) for this service...

Handler(s):"DEDICATED" established:0 refused:0 state:ready

REMOTE SERVER(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.2.9)(PORT=152 1))

"DEDICATED" established:0 refused:0 state:readyLOCAL SERVER

Instance "tpcc2", status READY, has 1 handler(s) for this service...Handler(s):

"DEDICATED" established:0 refused:0 state:readyREMOTE SERVER

(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.2.10)(PORT=15 21))


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The command completed successfully

--------------------------------------------------------------------------------------------After checking several connections using:

sqlplus "tpcc-at-tpcc/tpcc"

I could see the connections were being load balanced properly betweenthe two nodes.

Thanks a lot for your time guys! Seems the problem had to do withentries in tnsnames.ora and pfile.

- Sudhanshu


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RAC Networking,

Failover, and LoadBalancing

Setting up failover, loadbalancing, TAF and FCF

ObjectivesAt the end of this module the

student will understand the

following tasks and concepts.

Understand how Oracle Netinteracts with RAC.

Understand how to configuretnsnames for RAC with

Transparent Application Failover(TAF)

Understand how to configureJDBC connections for RAC


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Understand how to configureFast Connection Failover as an

alternative to RAC

Overview The Listener Configuration Files Oracle Net and RAC Connect-Time Failover TAF Failover Load Balancing

JDBC Configuration for Failoverand Load Balancing Fast Connection Failover

Listener

ClientNode 1

Node 2


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Database

Listener

Resides on the server Listens for incoming client

connection requests

Manages the traffic to theserver; when a client requests anetwork session with a server,the listener actually receives therequest and brokers the clientrequest

If the client's informationmatches the listener'sinformation, then the listenergrants a connection to theserver.

listener.ora


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Configuration file for the listenerprocess. Identifies:

o The listener name

o Protocol addresses that it willaccept connection requestson

o Services for which it islistening

Typically resides in the%ORACLE_HOME%\network\admin directory on Windows NT.

tnsnames.ora Configuration file that

determines how you connect tothe database.

o Connect to specific instanceo Load Balancingo Connect Time Failovero TAF Client Failover


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Must be present on server andthick clients (ODBC and JDBC

thick OCI driver)

Oracle Net and RAC

Oracle Netunderstands RAC Is used to set up thecluster behavior

Supports multiplemodes

o Connect-Time Failovero Load Balancingo TAF

Connect-Time Failover


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One serviceo Tries one nodeo then the other node

Used for failover Balance is done manually In the event of a failure

o Transaction is losto Session is losto Reconnection occurs

automatically

Connect-Time Failover TESTA1 = (DESCRIPTION= (ADDRESS_LIST= (LOAD_BALANCE=OFF) (FAILOVER=ON) (ADDRESS=(PROTOCOL=TCP)(HOST=oradb1)(PORT=1521)) (ADDRESS=(PROTOCOL=TCP)(HOST=oradb2)(PORT=1521))) (CONNECT_DATA= (SERVICE_NAME=TESTA) ) )

TESTA2 = (DESCRIPTION= (ADDRESS_LIST= (LOAD_BALANCE=OFF)


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(FAILOVER=ON) (ADDRESS=(PROTOCOL=TCP)(HOST=oradb2)(PORT=1521)) (ADDRESS=(PROTOCOL=TCP)(HOST=oradb1)(PORT=1521))) (CONNECT_DATA= (SERVICE_NAME=TESTA)

) )

Failover - Backup

Pairs of services

o The first service defines thesecond as its backup

o The second service definesthe first service as its backup

Used for RAC failover Balance is done manually In the event of a failure

o Transaction is losto Session is maintainedo Queries are restartedo Reconnection occursautomatically


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Failover Backup TESTA1 =

(DESCRIPTION = (ENABLE = BROKEN) (LOAD_BALANCE = off) (FAILOVER = on) (ADDRESS = (PROTOCOL = TCP)(HOST = oradb1)(PORT = 1523)) (CONNECT_DATA = (SERVICE_NAME = TESTA) (INSTANCE_NAME = TESTA1) (FAILOVER_MODE = (BACKUP = TESTA2) (TYPE = SELECT) (METHOD = BASIC) (RETRIES = 120) (DELAY = 5))))

TESTA2 = (DESCRIPTION = (ENABLE = BROKEN) (LOAD_BALANCE = off) (FAILOVER = on) (ADDRESS = (PROTOCOL = TCP)(HOST = oradb2)(PORT = 1523)) (CONNECT_DATA = (SERVICE_NAME = TESTA) (INSTANCE_NAME = TESTA2) (FAILOVER_MODE = (BACKUP = TESTA1) (TYPE = SELECT) (METHOD = BASIC) (RETRIES = 120) (DELAY = 5))))

Failover - Preconnect


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Pairs of serviceso The first service defines the second as

its backupo The second service defines the first

service as its backupo Both services preconnect to their

backup when the primary connectionsare made

Used for RAC failover Balance is done manually In the event of a failure

o Transaction is losto Session is maintainedo Queries are restartedo Connection is quickly switched over to

the preconnected backup

Failover - Preconnect TESTA1 = (DESCRIPTION = (ENABLE = BROKEN) (LOAD_BALANCE = off) (FAILOVER = on) (ADDRESS = (PROTOCOL = TCP)(HOST = oradb1-vip)(PORT = 1523)) (CONNECT_DATA = (SERVICE_NAME = TESTA) (INSTANCE_NAME = TESTA1) (FAILOVER_MODE = (BACKUP = TESTA2) (TYPE = SELECT)


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(METHOD = PRECONNECT) (RETRIES = 120) (DELAY = 5))))

TESTA2 = (DESCRIPTION = (ENABLE = BROKEN) (LOAD_BALANCE = off) (FAILOVER = on) (ADDRESS = (PROTOCOL = TCP)(HOST = oradb2-vip)(PORT = 1523)) (CONNECT_DATA = (SERVICE_NAME = TESTA) (INSTANCE_NAME = TESTA2) (FAILOVER_MODE = (BACKUP = TESTA1) (TYPE = SELECT) (METHOD = PRECONNECT) (RETRIES = 120) (DELAY = 5))))

Load Balancing

One serviceo Oracle Net determines which

node you use Tries to balance the load

Only active nodes are used Balance is somewhat random In the event of a failure

o Transaction is lost


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o Connection is lost

Load Balancing TESTA = (DESCRIPTION = (ADDRESS_LIST = (LOAD_BALANCE = on) (FAILOVER = off) (ADDRESS = (PROTOCOL =TCP)(HOST = oradb1-vip)(PORT= 1523))

(ADDRESS = (PROTOCOL =TCP)(HOST = oradb2-vip)(PORT= 1523))

) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = TESTA) ) )


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Transparent ApplicationFailover

One serviceo Multiple sessions are created

Only active nodes are used In the event of a failure

o available node is usedo No loss ofconnectiono Transaction is losto Query is restarted

Transparent ApplicationFailover

TESTA = (DESCRIPTION = (ENABLE = BROKEN) (ADDRESS_LIST = (LOAD_BALANCE = on) (FAILOVER = on) (ADDRESS = (PROTOCOL = TCP)(HOST = oradb1-

vip)(PORT = 1523))


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(ADDRESS = (PROTOCOL = TCP)(HOST = oradb2-vip)(PORT = 1523))

) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = TESTA) (FAILOVER_MODE = (TYPE = SELECT) (METHOD = BASIC) (RETRIES = 120) (DELAY = 5) ) ) )

Characteristics of TAF

TAF protects:o

Client/server connection

o User session stateo OCI programso Java thick drivers (OCI

drivers)o Sql*pluso Active cursors (select

statements) that have begunto return results

Not failed over:


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o Active update transactionso PL/SQL procedure stateso PL/SQL server-side packagevariableso alter session statementso Server side program

variableso Uncommitted transactions

Network Timeouts andTAF

When a planned instanceshutdown occurs, failover occursquickly

o Shutdown instance withsrvctl or OEM

o Failover takes a few seconds

When an unplanned instancefailure occurs, failover timing is


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sensitive to network timeoutparameters

o

Failover cannot occur untilthe network connection isreleased

o By default, it may take up toeight minutes for the networkconnection to be released

and for failover to occur Server-side and client-side

operating system level TCP/IPtimeout parameters may beshortened to speed up failover

o Failover can occur as quicklyas one minuteo Can increase risk of disrupted

network connections andunnecessary failover events


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Example Windows

TCP/IP TimeoutParameters for TAF

The following steps may beperformed on Windowsdatabase servers, mid-tier

servers, and clients to speed upfailover

o Open the registry hive underHKEY_LOCAL_MACHINE :SYSTEM CurrentControlSet :

Services : Tcpip : Parameterso Add KeepAliveTime :

REG_DWORD to the registryNote: The correct case isrequired for KeepAlive

o Set the value to a reasonable

timeout. Eg: (120000 = 2minutes, 60000 = 1 minute)


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JDBC Connections and

TAF

The Oracle JDBC thick driversupports TAF

o tnsnames,ora file must bedefined on the server-side

o JDBC Data Source file mustbe defined on the client-side(or mid-tier)

o TAF failover and loadbalancing are supported

The Oracle JDBC thin driver does

not fully support TAFo tnsnames,ora file must be

defined on the server-sideo JDBC Data Source file must

be defined on the client-side

(or mid-tier)o Load balancing is supported,

but not TAF failover


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JDBC Thick Driver

Example

JDBC Thin DriverExample


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o


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Fast Application

Notification

ONS and FastApplicationNotification

o The Oracle NotificationService provides a frameworkfor passing event messagesabout failover between nodes

o ONS may notify both RAC

nodes and client or mid-tiernodeso Fast Application Notification

provides the basis for FastConnection Failover

Fast ConnectionFailover


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Fast Connection Failoverprovides a way to control

failover response

o Effective for Oracle 10gApplication Server JDBCconnections

o More mid-tier applicationsmay be supported in the

futureo Works with JDBC Thick andJDBC Thin drivers

o Provides an alternative to TAFo Avoids network timeout

sensitivity

o Fast and efficient

Pre-requisites for Fast

Connection Failover The JDBC Implicit Connection

Cache is enabled.


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The application uses servicenames to connect to the

database, not service ids.

The database should be at leastrelease 10.1.0.2 (10.1.0.3 ispreferred).

ONS is configured and runningon the node where JDBC is

running. The JVM in which the JDBC

instance is running must haveoracle.ons.oraclehome set topoint to the ORACLE_HOME

where the ONS files wereinstalled.

Setting Up the Implicit

Connection Cache forFCF


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The following JDBC Data Source file sets upthe Implicit Connection Cache for FCF onthe Application Tier:

OracleDataSource ods = newOracleDataSource()

... ods.setUser(Scott); ods.setPassword(tiger); ods.setConnectionCachingEnabled(Tru

e); ods.setFastConnectionFailoverEnabled

(True); ods.setConnectionCacheName(MyCache); ods.setConnectionCacheProperties(cp); ods.setURL("jdbc:oracle:thin:@(DESCRIPTIO

N= (LOAD_BALANCE=on) (ADDRESS=(PROTOCOL=TCP)(HOST=VIP1)

(PORT=1521)) (ADDRESS=(PROTOCOL=TCP)(HOST=VIP2)

(PORT=1521)) (CONNECT_DATA=(SERVICE_NAME=service

_name)))");


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ONS on theApplications Tier

Edit the file%ORACLE_HOME%\opmn\conf\ons.config on each mid-tier node:

o localport=6100 # This is theport ONS is writing to on thisnode

o remoteport=6200 # This isthe port ONS is listening on

this node

o loglevel=3o # This is the list of hosts and

ports ONS is posting to.o # Include RAC and client

nodes.o nodes=RAC1.mycompany.co

m:6200,RAC2.mycompany.com:6200,


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o RAC3.mycompany.com:6200,APPS1.mycompany.com:6200

,

o APPS2.mycompany.com:6200

ONS on the

Applications Tier

When starting theapplication:

o Specify the system property

Doracle.ons.iraclehome=

o Include the ons.jar file in theapplication CLASSPATH


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Modifying Server-Side

ONS for FCF

Use the%ORA_CRS_HOME%\bin\racgonscommand to modify the server-side ONS configuration to be

aware of the mid-tier nodes:

o racgons add_configAPPS1.mycompany.com:6200APPS2.mycompany.com:6200

o This adds the host and portnames to the OCR

Differences betweenFCF and TAF


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Application-Level

ConnectionRetries.o Fast Connection Failover

supports application-levelconnection retries. This

gives the application controlof responding to connectionfailovers.

o TAF supports connectionretries only at the OCI/Netlayer.



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Integration with

the ConnectionCacheo Fast Connection Failover is

well-integrated with theImplicit Connection Cache,

which allows the connectioncache manager to managethe cache for HA.

o Failed connections areautomatically invalidated inthe cache.

o TAF works at the networklevel on a per-connectionbasis, which means that theconnection cache cannot benotified of failures.


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Differences between

FCF and TAF

Event-Basedo Fast Connection Failover is

based on the RAC eventmechanism. This means that

Fast Connection Failover isefficient and detects failuresquickly for both active andinactive connections.

o TAF is based on the network

call mechanism.


Load-BalancingSupport


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o Fast Connection Failoversupports UP event load

balancing of connections andruntime work requestdistribution across activeRAC instances.

Review

What are the two keyconfiguration files for OracleNet?

What key phrase in thetnsnames.ora file influencesloadbalance behaviour?

What key phrase in thetnsnames.ora file influencesfailover behaviour?

Which Oracle Net configurationsallow users to maintainconnections through a failoverevent?


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Which JDBC drivers aresupported under TAF and FCF?

What is the name of the utilityto add mid-tier nodes to theserver-side ONS configuration?

Summary

Listener process Configuration files

o listener.orao tnsnames.ora

Failover

o Basico Preconnect

Load Balancing TAF JDBC Thick and Thin drivers and

TAF Setting up Fast Connection

Failover


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The listener is a process that resides on the server whose responsibility is tolisten for incoming client connection requests and manage the traffic to theserver.

The listener brokers the client request, handing off the request to the server.

Every time a client (or server acting as a client) requests a network session witha server, a listener receives the actual request. If the client's information matchesthe listener's information, then the listener grants a connection to the server.

Oracle databases do not require identification of the database service inlistener.ora because of service registration. However, static service configurationis required for an Oracle databases if you plan to use a listener.

The tnsnames.ora (or the equivalent) must be used if you want to useTransparent Application Failover. There must be a copy located on each RACserver. In addition, key components of the server-side tnsnames.ora file must bepresent in a client-side tnsnames.ora file. However, for JDBC connections, thetnsnames.ora content is often contained in a long connection string in the JDBCconfiguration file on the client. Note that the JDBC driver for TAF must be theOracle supported thick OCI driver.


By setting up multiple network paths, OCI will try each of the paths in the connection list. In thismanner you can set up multiple nodes in the cluster, but at the same time, specifying which nodeis the primary connection. This can be done by putting the following entry into the tnsnames.orafile.

prod1.us.company.com =(DESCRIPTION=(ADDRESS_LIST=(LOAD_BALANCE=OFF)(FAILOVER=ON)(ADDRESS=(PROTOCOL=tcp)(HOST=prod1)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=prod2)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=prod1.us.company.com)))

prod2.us.company.com =(DESCRIPTION=(ADDRESS_LIST=(LOAD_BALANCE=OFF)


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In this example, there are two different service names. The first uses prod1 as the primary and prod2 as the failover, the seconduses prod2 as the primary and prod1 as the failover. Note the extended syntax under FAILOVER_MODE= as compared toconnect-time failover. This syntax is RAC specific, and allows the session state to be maintained through failover for queries(transactions are rolled back). The RETRIES and DELAY parameters allow the connection to be retried if the first attempt is not

successful.

Note that the IP addresses or host names used in the tnsnames.ora file shouldbe Virtual IP addresses or host names for Oracle 10g RAC.

Failover - Preconnect

Note that setting the METHOD = preconnect allows the backup connection to be pre-allocated. This can aid failover speed, at the cost of twice as many concurrent connections.

prod1.us.company.com =(DESCRIPTION =(LOAD_BALANCE = off)(FAILOVER = on)(ADDRESS = (PROTOCOL=tcp)(HOST=prod1)(PORT=1521))(CONNECT_DATA =

(SERVER = DEDICATED)(SERVICE_NAME = prod.us.company.com)

(INSTANCE_NAME = prod1.us.company.com)

(FAILOVER_MODE =(BACKUP = prod2.us.company.com)

(TYPE = select)

(METHOD = preconnect))))prod2.us.company.com =(DESCRIPTION =(LOAD_BALANCE = off)(FAILOVER = on)(ADDRESS = (PROTOCOL=tcp)(HOST=prod1)(PORT=1521))(CONNECT_DATA =

(SERVER = DEDICATED)(SERVICE_NAME = prod.us.company.com)

(INSTANCE_NAME = prod2.us.company.com)

(FAILOVER_MODE =(BACKUP = prod1.us.company.com)

(TYPE = select)

(METHOD = preconnect))))


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Load Balancing

Load balancing is similar to Connect-time Failover in that one service is definedwith multiple addresses. In this case, automatic load balancing is turned onwhile failover is turned off. This can be done by putting the following entry intothe tnsnames.ora file.

prod.us.company.com =(DESCRIPTION=

(ADDRESS_LIST=(LOAD_BALANCE=ON)(ADDRESS=(PROTOCOL=tcp)(HOST=prod1)(PORT=1521))(ADDRESS=(PROTOCOL=tcp)(HOST=prod2)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME=prod.us.company.com)))

Here either prod1 or prod2 will be used. The system used is determined atconnection time. Load balancing is commonly used with RAC, both in theserver-side tnsnames.ora file and the client-side tnsnames.ora file.


Transparent Application Failover (TAF)

The TAF mechanism provides some fault tolerance in the event of a node failure. It does this byestablishing a connection to multiple nodes in the cluster. TAF will automatically resend some

transactions, and will not result in the loss ofconnection to the user in the event of a failure. TAFis configured by specifying both FAILOVER and LOAD_BALANCE as shown here:

prod.us.company.com=(DESCRIPTION=(LOAD_BALANCE=on)(FAILOVER=on)(ADDRESS=

(PROTOCOL=tcp)


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(HOST=prod1)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=prod2)(PORT=1521))

(CONNECT_DATA=(SERVICE_NAME=prod.us.company.com)(FAILOVER_MODE=

(TYPE=select)(METHOD=basic))))

The TYPE parameter accepts the following options:

session - In this mode a new session is created on the failover server in the event of a failure.

select - Cursor processing is maintained. This incurs significant overhead on the client.

none (default) - No failover is done.

The METHOD parameter accepts the following options:

basic - establishes the connection to the failover server when it is needed.

preconnect - establishes the connection to the failover server at initial connection time.


What TAF Restores

TAF automatically restores some or all of the following elements associated with active database connections. Other elements,

however, may need to be embedded in the application code to enable TAF to recover the connection.

Client-Server Database ConnectionsTAF automatically reestablishes the connection using the same connect string or an alternate connect string that you specify

when configuring failover.

Users' Database Sessions

TAF automatically logs a user in with the same user ID as was used prior to failure. If multiple users were using the connection,then TAF automatically logs them in as they attempt to process database commands. Unfortunately, TAF cannot automatically

restore other session properties. These properties can, however, be restored by invoking a callback function.

Executed CommandsIf a command was completely executed upon connection failure, and it changed the s tate of the database, TAF does not resendthe command. If TAF reconnects in response to a command that may have changed the database, TAF issues an error message

to the application.

Open Cursors Used for FetchingTAF allows applications that began fetching rows from a cursor before failover to continue fetching rows after failover. This is


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called "select" failover. It is accomplished by re-executing a SELECT statement using the same snapshot, discarding those rowsalready fetched and retrieving those rows that were not fetched initially. TAF verifies that the discarded rows are those that were

returned initially, or it returns an error message

Active TransactionsAny active transactions are rolled back at the time of failure because TAF cannot preserve active transactions after failover. The

application instead receives an error message until a ROLLBACK is submitted.

Server-side Program VariablesServer-side program variables, such as PL/SQL package states, are lost during failures; TAF cannot recover them. They can be

initialized by making a call from the failover callback.

Note the failover=on, failover_mode=, and rac_enabled=true sections.

Note the LOAD_BALANCE=on is set, but failover is not set (TAF failover is notsupported with the thin driver).

The command %ORACLE_HOME%\opmn\bin\onsctl start can be used to startONS, and the command %ORACLE_HOME%\opmn\bin\onsctl stop can beused to stop ONS.

Do not modify the server-side ons.config file to add the mid-tier hosts and ports.This does not modify the OCR. Use the racgons command instead.

Note: The application should not try to roll back the transaction; the transactionwas already rolled back in the database by the time the application received theexception.You should not attempt to run both TAF and FCF at the same time.



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Oracle RAC Administration - Part 15: Connection LoadBalancing and FAN

Tarry Singh, [email protected]

Brief intro

In our last article, we looked at the service architecture. We will continue our quest to understandthe workload characteristics and the load balancing connections in our Virtualized RAC.

Introduction to Workload Management

Connection Load Balancing

With Oracle Notification Services (ONS), we are able to have our RAC balance our clientconnections across the nodes. The CLB (connection load balancing) can be handled on theserver-side or on the client-side. The client-side takes care of the connection sharing across theListeners, while server-side load balancing manages and handles the connection requests to themost willingly available node whose information is in turn provided to it by the LBA (LoadBalancing Advisory).

This in turn is analyzing the goals that may have been set for the LBA. You can use a long goal ora short goal for this connection load balancing. Lets take a look at them both quickly.

Long Goals: Use long goals for applications that need long uninterrupted connections. It is thedefault connection load balancing goal. To see how to implement them, lets take a simple syntax.Using the DBMS_SERVICE and CLB_GOAL_LONG packages, you can define the connection load

balancing for long connections as follows and here FOKESERV is our service:

EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name =>'FOKESERV'

, clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);

Short Goals: Think of quick and fast transactions like ordering or placing a secure purchase likethat on Amazon or any other place. You would prefer to fill the order up fast and if, for any reasonthe process is delayed, the connection is restarted, ensuring that the transaction is performed in a

short-lived connection. Checking the syntax, here CARTSERV is the service in question:

EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name =>'CARTSERV'

, CLB_GOAL => DBMS_SERVICE.CLB_GOAL_SHORT);

Note: When you install your RAC with the DBCA (Database Configuration Assistant), server-sideload balancing is enabled by default. Also check out the sample script in tnsnames.ora file. The
mailto:[email protected]:[email protected]


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services created through the DBCA will have the Connection Load Balancing default setting asCLB_GOAL=CLB_GOAL_LONG.

The ONS maintains client connections until the client decides to close the connection or if a nodefails or any other form of outage prevents the continuity of that connection. However, if youconfigure TAF (transparent application failover) then the connections are moved to another

healthy instance. For a typical SARG (Select Arguments), TAF can restart the query. Alternately,from the client side, if you were accessing information on the web, the search would simply carryon without you noticing the failover of the connection to another node. However, if you were in themiddle of a transaction (INSERT, UPDATE, or DELETE) then the application must rollback thefailed transaction and submit it again. Any other session's customizations must be re-executed.However, in a normal processing scenario the sessions dont move irrespective of the workloadchanges, newer sessions are just redirected to other nodes.

With the services, the deployment of TAF only becomes easier. By defining a TAF policy for aservice, all connections using this service will have TAF automatically enabled for them. No client-side intervention is required, meaning the server-side TAF setting will override the TAF setting atthe client level. In order to define the TAF policy you will need the DBMS_SERVICE procedure:

EXECUTE DBMS_SERVICE.MODIFY_SERVICE (service_name =>'fokeserv.domain.com', aq_ha_notifications => TRUE, failover_method => DBMS_SERVICE.FAILOVER_METHOD_BASIC, failover_type => DBMS_SERVICE.FAILOVER_TYPE_SELECT, failover_retries => 180, failover_delay => 5, clb_goal => DBMS_SERVICE.CLB_GOAL_LONG);

Client-side load balancing is defined in your client connection with the parameterLOAD_BALANCE=ON (the default is ON). Upon setting this parameter to ON, Oracle will pick out an

address from the address list at random and connect to that node, thereby balancing the clientconnections across the cluster. Run the command lsnrctl services occasionally to see what

services a listener supports.

FAN (Fast Application Notification)

As the Oracle RAC manual states:

FAN is a notification mechanism that RAC uses to notify other processes about configuration andservice level information such as includes service status changes, such as UP or DOWN events.

Applications can respond to FAN events and take immediate action. FAN UP and DOWN eventscan apply to instances, services, and nodes.

RAC publishes the FAN events the minute any changes are made to the cluster. So, instead ofwaiting for the application to check on individual nodes to detect an anomaly, the applications arenotified by FAN events and are able to react immediately.

FAN also publishes load balancing advisory (LBA) events. Applications are in a position to takefull advantage of the LBA FAN events to facilitate a smooth transition of connections to healthiernodes in a cluster. One can take advantage of FAN is the following ways:


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When using integrated Oracle Client, the applications can use FAN with no

programming whatsoever. Oracle 120g JDBC, ODP.NET and OCI would beconsidered as the components of the integrated clients.

Programmatic changes in ONS API make it possible for applications to still

subscribe to the FAN events and can execute the event handling actionsappropriately.

FAN can be implemented with server-side callouts on your database tier.

For instance, a typical DOWN event will prevent any further disruption of service by cleanly

terminating the sessions on that failed node and notifying the user. Moreover, a typical UP event

can address and allocate extra resources for new incoming requests/ connections. There arehowever several additional benefits with the server-side callouts, mainly you can utilize FAN inorder to:

Logging

Paging/SMS the DBA and/or to open trouble tickets when the resources fail

to (re)start Change resource plans or to shut down services when the number of

available instances decreases, thus preventing further load on the clusterand keeping the RAC running until another healthy node is added to thecluster.

Automate the fail service back to PREFERRED instances when required.

Conclusion

In this article, we looked at the CLB and FAN. In future articles, we will continue to discuss theservices architecture and discuss FAN in detail and take a look at the LBA.

Oracle RAC Administration - Part 16: Balancing act

between Server and Client

Brief intro

We will take a little detour from our regular path of following the manual, some would say, to morepractical path. One topic that most intrigues both an Oracle DBA and their clients (in their ownway) is connectivity. DBAs are sometimes puzzled with the load balancing and failover part ofconnectivity. Where is it, on the Client-side OR the Server-side? Is tnsnames.ora still useful if Ideploy the Easy Connect Net Naming method? Let's brush up on some basics.

Easy Connect Naming Methods

Easy Connect Naming methods were introduced in Oracle 10g. The benefits were simple. Theneed to do a service name lookup in the tnsnames.ora files for TCP/IP environment waseliminated, a directory naming system is no longer needed and clients are connectedautomatically. Connecting is also fairly simple:

Syntax:

CONNECT username/password@[//]host[:port][/service_name]


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So our typical examples could look like:

CONNECT oe/oe@localhost/nickservCONNECT scott/[email protected]/examples


From the clients end, when your connection fails at one node or service, you can then do a lookup from your tnsnames.ora file and go on seeking a connection with the other available node.Take this example of our 4-node VMware ESX 3.x Oracle Linux Servers:

FOKERAC =(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST =

nick01.wolga.com)(PORT = 1521))(ADDRESS = (PROTOCOL = TCP)(HOST = nick02.wolga.

com)(PORT = 1521))

(ADDRESS = (PROTOCOL = TCP)(HOST = brian01.wolga.com)(PORT = 1521))(ADDRESS = (PROTOCOL = TCP)(HOST = brian02.wolga.

com)(PORT = 1521))(CONNECT_DATA =(SERVICE_NAME = fokerac)

))

Here the first address in the list is tried at the clients end. Should the connection tonick01.wolga.nl fail, then the next address, nick02.wolga.nl, will be tried. This phenomenon iscalled connection-time failover. You could very well have a 32-node RAC cluster monitoring the

galactic system at NASA and thus have all those nodes typed in your tnsnames.ora file.Moreover, these entries do not necessarily have to be part of the RAC cluster. So it is possiblethat you are using Streams, Log Shipping or Advanced Replication to maintain your HA (HighAvailability) model. These technologies facilitate continued processing of the database by such aHA (High Availability) model in a non-RAC environment. In a RAC environment we know (andexpect) the data to be the same across all nodes since there is only one database.

TAF (Transparent Application Failover)

Transparent Application Failover actually refers to a failover that occurs when a node or instanceis unavailable due to an outage or other reason that prohibits a connection to be established onthat node. This can be set to on with the following parameter FAILOVER. Setting it to ON willactivate the TAF. It is turned on by default unless you set it to OFF to disable it. Now, when youturn it on you have two types of connections available by the means of the FAILOVER_MODEparameter. The type can be session, which is default or select. When the type is SESSION, if theinstance fails, then the user is automatically connected to the next available node without theusers manual intervention. The SQL statements need to be carried out again on the next node.However, when you set the TYPE to SELECT, then if you are connected and are in the middle ofyour query, then your query will be restarted after you have been failed over to the next availablenode. Take this example of our tnsnames.ora file, (go to the section beginning withCONNECT_DATA):


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(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = fokerac.wolga.com)(FAILOVER_MODE =(TYPE = SELECT)

(METHOD = BASIC)(RETRIES = 180)(DELAY = 5))

)

This is also demonstrated in thisimage from my article on Quests soRAC tool.

This is more intelligent in the sense that should the instance, (where the user has fired a query),go down then the session will remember the rows in its Global Buffer Cache, restart the queryand pick up from where the user left off when they were disconnected from the first node.

Compare it to a scenario where the manager is running the query through a client such as CrystalReports or Oracle Reports. Running the monthly query to get the data from his Server Monitoringsoftware, let's say NetIQ, to get the statistics of all the servers the DBA needs to draw a report onmonitoring the CPU, memory or disk usage. Now if he ran a query that had to fetch 5000 rowsand he gets cut off at 3000 rows, he still has to reissue (not manually though) start from thebeginning but will only see the results when he crosses the 3001 mark. Then upon prompt, theresults will be shown. However, this does not apply to the DML (Data Manipulation Language)such as insert, update, delete. The user is met with an error if node failure happens in the middleof the processing and all the (uncommitted) transactions are rolled back. The session eventuallyfails over without the user having to connect, however, he does have to issue the query again.

Preconnect Method

Consider our tnsnames.ora file again. Here in our older example, where the METHOD wasBASIC, there is some additional time loss in reconnecting the lost connection to the immediateavailable node. However, when you set the METHOD to PRECONNECT, a session is connectedto all available nodes in the list. The advantage is that failover is a lot quicker than the BASICmethod but the downside is that the other instances will continue to claim necessary resourcessuch a system memory to keep those connections alive.

(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = fokerac.wolga.com)(FAILOVER_MODE =(TYPE = SELECT)

(METHOD = PRECONNECT)(RETRIES = 180)(DELAY = 5))

)
http://www.dbasupport.com/img/ts_soRAC1_image002.jpghttp://www.dbasupport.com/img/ts_soRAC1_image002.jpghttp://www.dbasupport.com/img/ts_soRAC1_image002.jpg


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Conclusion

As a DBA, these little things are very crucial in deciding what you intend to do with the RAC. Is ita DSS or will it be used for a heavy OLTP environment. On a DSS, you can easily choose aPRECONNECT method as you expect to have less connections with long durations (batchprocessing, etc.) where as a typical OLTP will perform better if the cluster is optimally configured

with a BASIC method.

Oracle 10g Rac Load Balance Connection

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