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Overview of Oracle Net
Setup
Oracle Tips by Burleson
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There are several files that must either be
set up manually or can be setup via the Oracle Net Configuration
Assistant. These are divided between the server and the client.
Server Oracle Net Files
On the server the listener.ora, sqlnet.ora and
maybe the onames.ora files need to be configured depending on whether
Oracle Names is being used or not. If other options such as LDAP are
configured other files may also be required.
The
Listener.ora File
The Listener.ora file tells the listener what
instances are available for connection on the server. Beginning in
Oracle8i the instances will auto-register when they start if the
listener is started. This auto registration of database instances
means you no longer have to populate the listener.ora file with
entries when new instances are added to a server. However, this is
only for Oracle8i and greater versions of Oracle, all other versions
of Oracle must be manually entered into the file either via an editor
or through the GUI interface provided.
Before you can configure the listener.ora file
you must decide whether you want to use a flat model for your Oracle
instance structure or the structured model. If you use the flat model
(suggested for small Oracle installations where there aren't multiple
databases, divisions or offices) then your instance tree begins at
WORLD as the root and ends with WORLD, essentially more of an instance
lawn than an instance tree.
On the other hand, if you have multiple
databases spread across multiple divisions and offices then a more
structured instance tree is required. For a more structured instance
tree begin with the name of the company or organization as the root of
the tree, then each office becomes a branch as does each division
inside each office, finally the leaves of the tree are the database
instances. The structured instance network is similar to the structure
of the internet, except, while the address in the internet would be
www.pubs.com an example instance address in Oracle would be consult.chicago.pubs where consult is the instance name, Chicago is
the office and pubs is the company. Before beginning to setup the
listener.ora file for each office or division you would need to know
where on the instance hierarchy it falls.
For example for my test environment I have
chosen a root of PUBS, main branches will be the server or computer
names and the end leaves will of course be the database name. I have a
LINUX server called PUBSGALINUX and a laptop called MRAMOBILE. On
PUBSGALINUX I have a database GALINUX1 and on MRAMOBILE I have a
database called AULTDB1. Figure 14.2 shows what this configuration
looks like graphically.
Figure 14.2 Graphic Representation of Example
Network.
The listener.ora file for the PUBSGALINUX
Oracle host is shown in listing 14.1.
LISTING 14.2 Example Listener.ora File
#
LISTENER.ORA Network Configuration File: /var/oracle/OraHome2/network/admin/listener.ora
# Generated by Oracle configuration tools.
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST =
pubsgalinux)(PORT = 1521))
)
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /var/oracle/OraHome2)
(PROGRAM = extproc)
)
(SID_DESC =
(GLOBAL_DBNAME =
galinux1.pubsgalinux.pubs)
(ORACLE_HOME = /var/oracle/OraHome2)
(SID_NAME = galinux1)
)
)
After configuring the listener.ora file, the
listener process needs to be started. On LINUX and UNIX the lsnrctl
program is used to start, stop and reload the listener. On Windows
based platform the command line version of this program can be used or
the service can be stopped and restarted from the control panel
services icon. If the listener process is already running (use:
lsnrctl status listener_name to find out, default listener name is
listener) then you can issue a reload command to reread the
listner.ora for all changes except a change in the listing port. To
start a listener process the command:
oracle@pubsgalinux:
lsnrctl start
is issued where the appropriate listener name
is appended to the command if other than listener is used. To stop a
listener process the command:
oracle@pubsgalinux:
lsnrctl stop
is issued where the appropriate listener name
is appended to the command if other than listener is used.
Once the listener file is established and the
listener process is running the tnsnames.ora file needs to be
populated with the connection information for all databases that you
wish to connect with from the server or client. An example
tnsnames.ora file for the example network is shown in listing 14.2.
LISTING 14.3 Example tnsnames.ora file
#
TNSNAMES.ORA Network Configuration File: /var/oracle/OraHome2/network/admin/tnsnames.ora
# Generated
by Oracle configuration tools.
EXTPROC_CONNECTION_DATA.LOCAL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)
AULTDB1.MRAMOBILE =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL =
TCP)(HOST = mramobile)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = aultdb1.mramobile.pubs)
)
)
AULTDB1.LOCAL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL =
TCP)(HOST = mramobile)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = aultdb1.mramobile.pubs)
)
)
GALINUX1.LOCAL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = pubsgalinux)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = galinux1.pubsgalinux.pubs)
)
)
INST1_HTTP.PUBSGALINUX =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = pubsgalinux)(PORT = 1521))
)
(CONNECT_DATA =
(SERVER = SHARED)
(SERVICE_NAME = MODOSE)
(PRESENTATION = http://HRService)
)
)
Notice in listing 14.2 that there is a listing qualified with
either local or the host value for each database. The listener will
attach the value specified in the sqlnet.ora parameter
NAMES.DEFAULT_DOMAIN to any unqualified name, so GALINUX1 becomes
GALINUX1.LOCAL if it cannot locate an unqualified name, or one that
matches the sid.default_domain, then it will try to resolve the name
based on the order of naming method values in the sqlnet.ora parameter
NAMES.DIRECTORY_PATH which defaults to TNSNAMES, ONAMES, HOSTNAME. An
example sqlnet.ora file is shown in listing 14.3
LISTING 14.4 Example SQLNET.ORA file.
# SQLNET.ORA
Network Configuration File: /var/oracle/OraHome2/network/admin/sqlnet.ora
# Generated
by Oracle configuration tools.
NAMES.DEFAULT_DOMAIN = local
NAMES.DIRECTORY_PATH= (TNSNAMES, ONAMES, HOSTNAME)
As you can see from examining Listing 14.3,
there isn't much to a SQLNET.ORA default file, however, this file can
be used to add auditing and tracing options.
Connectivity to a remote or local database can
be tested using the tnsping program. To use the tnsping program you
simply issue the tnsping command followed by the sid of the database
you for which you wish to test connectivity.
Oracle Net Configuration Assistant
I have mentioned the Oracle Net Configuration
assistant (NETCA) several times in the last few sections. The NETCA is
a Java based GUI that makes configuring and testing Oracle Net
connections very easy. Figure 14.x shows the top level screen of the
NETCA GUI. If you are only configuring a simple Oracle Net setup there
are only two options on this NETCA GUI you will need to bother with,
for the server setup you will use the Listener Configuration and Local
Net Service Name Configuration options, for the client, you need only
use the Local Net Service Name Configuration option.
The NETCA GUI can be invoked from the command
line using netca as the command, from the OEM Service Manager - Oracle
Net manager selection or in Windows from the
Start-Programs-Oracle-Network Administration menu. The OEM Oracle net
manager is shown in Figure 14.xx. In The OEM Oracle Net manager for a
simple topology you should just use the Profile, Service naming and
Listeners configuration options under the Local configuration icon.
The top level screen for the Oracle net Configuration Assistant is
shown in Figure 14.3. The top level screen of the OEM Oracle net
manager is shown in Figure 14.4
Figure 14.3 Top Level NETCA GUI Screen
The interfaces are really rather intuitive
once you get into them and understand exactly what you want to do. I
suggest overlooking the Oracle Net manuals before attempting to
configure your system if it is more complex than a couple of
databases, a server and a flat network topology.
Figure 14.4 Top Level OEM Net Manager GUI Screen
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