OCA 05 - Configuring the Oracle Network Environment

05 - Configuring the Oracle Network Environment

By Muhammad Asghar Khan

Reference: OCA Oracle Database 11g - Admin I Exam Guide by John Watson

http://asghars.blogspot.com2

Agenda Configure and Manage the Oracle Network

Oracle Net Establishing a Session Methods of Name Resolution Listener Net Manager TNS Ping Database Links EXERCISE 5-1 Configure Oracle Net

Use the Oracle Shared Server Architecture EXERCISE 5-2: Set Up a Shared Server Environment

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Configure and Manage the Oracle Network Oracle calls its set of connectivity solutions Oracle

Net Oracle Net

In the Oracle environment, no user has direct access to the database

A user interacts with a user process (e.g. SQL *Plus) The server process is a process running on the

database server machine that executes the SQL it receives from the user process

The execution of a SQL statement goes through four stages: parse, bind, execute, and fetch

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Configure and Manage the Oracle Network Parse Phase

Server process works out what the statement actually means, and how best to execute it

Bind Phase Any variables used in SQL statement are expanded to

literal values Execute Phase

Data in the database buffer cache will be read or updated and changes written to the redo log buffer

If the relevant blocks are not in the database buffer cache, server process will read them from the datafiles

This is the only point in the execution of a statement where the database itself is involved

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Configure and Manage the Oracle Network Fetch Phase

The server process sends the result set generated by the statement’s execution back to the user process, which should then format it for display

Oracle Net provides the mechanism for launching a server process to execute code on behalf of a user process, this mechanism is called establishing a session

A user interacts with a user process; a user process interacts with a server process, via Oracle Net; a server process interacts with the instance; and the instance, via its background processes, interacts with the database

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Configure and Manage the Oracle Network Oracle Net is a layered protocol: it runs on top of

whatever communications protocol is supported by your operating system

These protocols may include TCP, TCP with secure sockets, Windows Named Pipes (or NMP), and the newer Sockets Direct Protocol (or SDP) over Infiniband high-speed networks

For local connections where the user process is on the same machine as the server Oracle Net uses the Inter –Process Communication (or IPC) protocol

Oracle Net maps on to layers five, six, and seven: the session, presentation, and application layers of OSI model

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Configure and Manage the Oracle Network Establishing a Session

When a user, through his user process, wishes to establish a session against an instance, he will issue a command something likeCONNECT SCOTT/TIGER@ORCL

The database user name (“SCOTT”), and password (“TIGER”) are separated by a “/” as a delimiter

The “@” symbol is followed by a connect string “ORCL”

The “@” symbol is an indication to the user process that a network connection is required to an instance on a remote machine

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Configure and Manage the Oracle Network If the “@” and the connect string are omitted, then

the user process will assume that the instance you wish to connect to is running on the local machine, and that the always-available IPC protocol can be used

Local instance connection does not require a database listener; indeed, local connections do not require any configuration at all

The only information needed is to tell your user process which instance you want to connect to

You give the process this information through an environment variable

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Configure and Manage the Oracle Network If your connect statement includes the connect string

“@orcl,” Oracle Net has to work out what is meant by “orcl”, this is calle name resolution

This means that the string has to be resolved into certain pieces of information: Protocol you want to use, IP address/Host name on which the database listener is

running, Port that the listener is monitoring for incoming

connection requests, and the Name of the instance /service

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Configure and Manage the Oracle Network Methods of Name Resolution

Oracle provides four methods of name resolution: easy connect, local naming, directory naming, and external naming

Easy Connect It is limited to one protocol: TCP Easy Connect cannot be used with any of Oracle Net’s more

advanced capabilities such as load balancing or connect-time failover across different network routes

DBA find it very handy to use, but it is not a method of much use for your end users

You invoke it with a syntax such as this as your connect string:

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Configure and Manage the Oracle Network connect scott/[email protected]:1522/orcl SQL*Plus will use TCP to go to port 1522 on the IP address to

which the hostname resolves Then if there is a listener running on that port and address, it

will ask the listener to spawn a server process against an instance that is part of the service called orcl

Local Naming With local naming the user supplies Oracle Net service alias for

the connect string, and the alias is resolved by a local file (tnsnames.ora) into the full network address (protocol, address, port, and service or instance name)

The tnsnames.ora file is a client-side Consider this example of a tnsnames.ora file:

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Configure and Manage the Oracle Networkorcl = (DESCRIPTION =

(ADDRESS_LIST =(ADDRESS =

(PROTOCOL = TCP)

(HOST = pwr.financekpp.gov.pk)

(PORT = 1522))

)

(CONNECT_DATA = service_name = orcl)

)

) The alias orcl what your users will provide in their connect

statements Local naming supports all protocols and all the advanced

features of Oracle Net, but maintaining tnsnames.ora files on all your client machines can be an extremely time-consuming task

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Configure and Manage the Oracle Network Directory Naming

Directory naming points the user toward an LDAP directory server to resolve aliases

Oracle provides an LDAP server (the Oracle Internet Directory) as part of the Oracle Application Server, but you do not have to use that—if you already have a Microsoft Active Directory

Directory naming supports all Oracle Net features External Naming

It is conceptually similar to directory naming, but it uses third-party naming services such as Sun’s Network Information Services (NIS+) or the Cell Directory Services (CDS)

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Configure and Manage the Oracle Network Listener

When a client request reached the listener, the listener selects an appropriate service handler (a dispatcher or dedicated server) to service the client’s request and forwards the client’s request to it

The listener configuration is stored in a configuration file named listener.ora. Whose default location is the $ORACLE_HOME/network/admin directory

A listener spawn server processes against an instance In order to do this, it needs to know what instances are

available on the computer on which it is running A listener finds out about instances by the process of

“registration”

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Configure and Manage the Oracle Network There are two methods for registering an instance

with a database: static and dynamic Static Registeration

For static registration, you hard-code a list of instances in the listener.ora file

If you have older databases (prior to 8i) that your listener must connect users to, you will have to register them statically

Also some applications may require static registration: typically management tools

To register an instance statically, add an appropriate entry to the listener.ora file:

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Configure and Manage the Oracle Network SID_LIST_LIST2 = (SID_LIST = (

SID_DESC = (ORACLE_HOME =

/u01/oracle/app/product/11.2.0/db_1) (SID_NAME = orcl))

)

This entry configure the listener called LIST2 to accept connection requests for an instance called orcl

The directive ORACLE_HOME is only required if the database listener is not running from the same Oracle Home as the instance

This directive will let the listener find the executable file that it must run to launch a server process

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Configure and Manage the Oracle Network Dynamic Registration

This is the preferred method by which an instance will register with a listener

Dynamic registration requires no configuration at all if your listener is running on the default port, 1521

The initialization parameter local_listener, tells the instance the network address that it should contact to find a listener with which to register

At instance startup time, the PMON process will use this parameter to locate a listener, and inform it of the instance’s name and the names of the service(s) that the instance is offering

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Configure and Manage the Oracle Network The instance name is defined by the instance_name parameter, and the service_names parameter will have defaulted to this suffixed by the db_domain parameter

You will need to register your instance with the listener with “alter system register” if you have restarted the listener, or if you started the database instance before starting the listener

If your listener is not running on the default port on the address identified by the hostname, you must specify where the listener is by setting the parameter local_listener and reregistering

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Configure and Manage the Oracle Network alter system set local_listener=list2;

alter system register;

You can start and stop listeners through Database Control, but there is also a command-line utility lsnrctl

lsnrctl start [listener name] The STATUS command provides basic status information

about a listenerlsnrctl status [listener name]

The SERVICES command provides detailed information about the services and instances registered with a listener and the service handlers allocated to each instance

lsnrctl services [listener name]

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Configure and Manage the Oracle Network Net Manager

It is a stand-alone Java utility, shipped with all the Oracle client-side products

Use the net manager, to configure the clients to use the desired name resolution method

To launch the net manager run netmgr from an OS prompt

The net manager navigation tree has three branches:

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Configure and Manage the Oracle Network Profile

It is used to set options that may apply to both the client and server sides of Oracle Net and can be used to influence the behavior of all Oracle Net connections

When you take the Profile branch you are in fact configuring a file called sqlnet.ora

Sqlnet.ora contains settings that apply to all connections and listeners, such as security rules and encryption

There are defaults for every sqlnet.ora directive—but you will usually configure it if only to select the name resolution method

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Configure and Manage the Oracle Network Service Naming

It is used to configure client-side name resolution It edits the Local Naming tnsnames.ora file This file exists in your ORACLE_HOME/network/admin

directory Listeners

Listeners branch is used to configure database listeners

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Configure and Manage the Oracle Network TNS Ping

To test a connect string, use the TNSPING utility

tnsping orcl This will accept a connect string, locate the Oracle

Net files, resolve the string, and send a message to the listener

If the listener is running and does know about the service requested, the test will return successfully

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Configure and Manage the Oracle Network Database Links

Oracle Net can also be used for communications between databases

A user session against one database can execute SQL statements against another database

This is done through a database link Simple example of database link creation is: create database link prodscott connect to scott identified by tiger using 'prod';

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Configure and Manage the Oracle Network This defines a database link from the current

database to a remote database identified by the connect string PROD

You can issue statement through a link as select * from emp@prodscott;

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EXERCISE 5-1 Configure Oracle Net1. Create a directory to be used for the Oracle Net

configuration files, and set the TNS_ADMIN variable to point to this

2. Start the Net Manager. The top line of the Net Manager window will show the location of the Oracle Net files. If this is not the new directory, then the TNS_ADMIN variable has not been set correctly

3. Create a new listener: expand the Local branch of the navigation tree, highlight Listeners, and click the +

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EXERCISE 5-1 Configure Oracle Net4. Enter a listener name, NEWLIST, and click OK

5. Click Add Address

6. For Address 1, choose TCP/IP as the protocol and enter 127.0.0.1 as the host, 2521 as the port

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EXERCISE 5-1 Configure Oracle Net7. Create a new service name: highlight Service

Naming in the navigation tree, and click the +

8. Enter NEW as the net service name, and click Next

9. Select TCP/IP as the protocol, and click Next

10. Enter 127.0.0.1 as the host name and 2521 as the port and click Next

11. Enter SERV1 as the Service Name, and click Next. Click Finish

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EXERCISE 5-1 Configure Oracle Net

12. Save the configuration by clicking File and Save Network Configuration. This will create the listener.ora and tnsnames.ora files in the TNS_ADMIN directory

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EXERCISE 5-1 Configure Oracle Net13. Use an editor to check the two files

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EXERCISE 5-1 Configure Oracle Net14. Start the listener with lsnrctl

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EXERCISE 5-1 Configure Oracle Net15. From an operating system prompt, test the

connect string with tnsping new

16. Connect to your database using operating system authentication, bypassing any listener

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EXERCISE 5-1 Configure Oracle Net17. Set the service_names and local_listener

parameters for the running instance and register the new service name with the new listener

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EXERCISE 5-1 Configure Oracle Net18. From an operating system prompt, confirm that

the new service has registered with the new listener

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EXERCISE 5-1 Configure Oracle Net19. Confirm that the new network environment is

functional by logging on

system/oracle@new

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Use the Oracle Shared Server Architecture As more users log on to your instance, more server

processes get launched The database listener can launch as many processes

as required If you have a large number of concurrent

connection requests, your listener will have to queue them up

You can avoid this by running multiple listeners on different ports, and load-balancing between them

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Use the Oracle Shared Server Architecture But your operating system may well have limits on

the number of processes that it can support, limits to do with context switches and with memory

A computer can only do one thing at once unless it is an SMP machine, in which case each CPU can only do one thing at once

The operating system simulates concurrent processing by using an algorithm, often referred to as a time slicing or time-sharing algorithm

Context switches are very expensive

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Use the Oracle Shared Server Architecture As more users connect to the instance, the operating

system has to context-switch between more and more server processes

There may also be memory problems that occur as more sessions are established

The PGA is a block of memory associated with each server process, to maintain the state of the session and as a work area for operations such as sorting rows

This is why your system may begin to swap as more users log on

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Use the Oracle Shared Server Architecture There comes a point, performance begins to

degrade because of operating system inefficiencies in managing context switches and paging

These are not Oracle’s problems, but to overcome them Oracle offers the option of the shared server architecture

Shared server is implemented by additional processes that are a part of the instance

There are two new process types: dispatchers and shared servers

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Use the Oracle Shared Server Architecture The dispatchers run on a unique TCP port When a user process contacts a listener the listener

passes back the address of a dispatcher When a user process issues a SQL statement, it is sent to

the dispatcher The dispatcher puts all the statements it receives onto a

queue This queue is called the common queue, because all

dispatchers share it All the shared server processes monitor the common

queue

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Use the Oracle Shared Server Architecture From then execution proceeds through the usual

parse-bind-execute cycle, but when it comes to the fetch phase the shared server puts the result set onto a response queue that is specific to the dispatcher that received the job

Each dispatcher monitors its own response queue, and whenever any results are put on it, the dispatcher will pick them up and fetch them back to the user process that originally issued the statement

The state of the session is maintained in SGA

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Use the Oracle Shared Server Architecture The memory used in the SGA for each shared server

session is known as the user global area (UGA) and includes all of what would have been in a PGA with the exception of the session’s stack space

Shared server configuration needs two set dispatchers and shared_servers parameters

shared_servers controls the number of shared servers that will be launched at instance startup time

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Use the Oracle Shared Server Architecture The dispatchers parameter controls how many

dispatcher processes to launch at instance startup time, and how they will behave

To enable the shared server architecture, adjust the two critical parameters as follows:

alter system set

dispatchers='(dispatchers=2)(protocol=tcp)';

alter system set shared_servers=20;

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EXERCISE 5-2: Set Up a Shared Server Environment1. Continues from Exercise 5-1

2. Set the dispatchers and shared_servers parameters and register with the listener as follows

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EXERCISE 5-2: Set Up a Shared Server Environment3. Confirm that the dispatchers and shared servers

have started by querying the view V$PROCESS. Look for processes named S000, S001, S002, S003, D000, and D001:

4. From an operating system prompt, confirm that the dispatchers have registered with the listener

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EXERCISE 5-2: Set Up a Shared Server Environment

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OCA 05 - Configuring the Oracle Network Environment

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