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  • 1. Creating a tnsnames.ora file Networking TipsCreating a tnsnames.ora fileYou can create a tnsnames.ora file using nothing more spectacular than Notepad or (if youare that way inclined, and using a Unix box) vi, pico or any other text editor of your choice.The point is, tnsnames is just a text file, and any old text editor will do the job.However (and it’s a big one!), the tnsnames file has a syntax that’s rather tricky at thebest of times, and you’d be much better advised to use the Net8 Configuration Assistant todo the deed. It will prompt you for various bits of information, and then construct afunctioning tnsnames.ora file for you. Once you’ve got that, any small bits of editing youmight need to do are easy to perform in a text editor.To run the Configuration Assistant on Windows, just select [Start] [Programs] [Oracle –Oracle Home name] [Network Administration] [Oracle Net8 Configuration Assistant]. OnUnix, you just type netca from $ORACLE_HOME/bin to launch the same tool (if thatdirectory is in your PATH, of course, you can run it from anywhere).Incidentally, for Oracle 9i on Windows, the location of the program changed (just to keepyou on your toes, you understand!). Try: [Start] [Programs] [Oracle – Oracle Home name][Configuration and Migration Tools] [Net Configuration Assistant]. It’s the same tool as in8i when you finally get there!Finally, note that in 8i there’s another option in Windows called “Net8 Assistant” (in 9i,it’s called “Net Manager”). I’d advise you not to use this option: it does the same job asthe Net8 Configuration Assistant, but assumes you know what you are doing, and that youknow how to navigate your way to precisely the right bit of the Net8 architecture to dosome configuration work. It’s not Wizard-driven, in other words; and when you’re juststarting out, the hand-holding of the Wizard can be quite helpful. By all means, if you arealready a Net8 Guru, use the more advanced tool –it’s quicker, in some respects- but if youare already a Guru, I’d question why you’re reading this paper in the first place!Anyway, let’s assume you’ve fired up the Net8 Configuration Assistant (or its 9i equivalent).You’ll see something that looks like this:Copyright © Howard Rogers 2002 3/17/2002 Page 1 of 14
  • 2. Creating a tnsnames.ora file Networking TipsSo the first thing you’ll notice about this tool is that it is something of a one-stop shop: youcan use it to create not only tnsnames.ora, but new Listeners (i.e., listener.ora) and newsqlnet.ora files too.Since tnsnames.ora is a local naming method, we need the third option from this screen(“Local Net Service Name configuration”). Select that, and click [Next].If this is the first time you’ve invoked the tool, your only available option now will be to“Add”. The other options are available only if you’re using the tool to edit a previously-created tnsnames.ora. Assuming “Add” is selected, click [Next].Copyright © Howard Rogers 2002 3/17/2002 Page 2 of 14
  • 3. Creating a tnsnames.ora file Networking TipsYou need to specify whether you are trying to connect to an 8.0 (or 7.0) database, or an 8i(and above) version. The difference is that in 8i, Oracle introduced the ability for anInstance to register itself automatically with the Listener. Before that, Instance nameshad to be manually configured. So the selection here is really a matter of whether thatextra configuration needs to be prompted for. I’m going to assume that you’re workingwith 8i and above (if you’re not, it’s time to upgrade).The first potentially hazardous screen! You need to specify which Instance you want toconnect to. The screen suggests that you should normally enter the global database name,which is constructed from the DB_NAME and the DB_DOMAIN parameters of your database’sCopyright © Howard Rogers 2002 3/17/2002 Page 3 of 14
  • 4. Creating a tnsnames.ora file Networking Tipsinit.ora. In my case, that would be “db9.aldeburgh.local” (because my DB_DOMAINhappens to be set to ‘aldeburgh.local’) but, as you can see, I’ve trimmed that down to just“db9”, because I want to illustrate what happens when you confuse the global databasename with the friendly alias that you usually get familiar with as the connection identifier.On page 6, you’ll see what happens when you don’t specify the right service name as aresult of this (quite common) error.Incidentally, it’s quite easy to determine what name should actually go here. If you go tothe server, and (at a command prompt) type lsnrctl services, you’ll see something thatlooks like this:C:Documents and SettingsAdministrator>lsnrctl servicesLSNRCTL for 32-bit Windows: Version 9.0.1.1.1 - Production on 17-MAR-2002 08:45:56Copyright (c) 1991, 2001, Oracle Corporation. All rights reserved.Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=mozart)(PORT=1521)))Services Summary...Service "db9.aldeburgh.local" has 3 instance(s). Instance "db9", status UNKNOWN, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 LOCAL SERVER Instance "db9", status READY, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:0 refused:0 state:ready LOCAL SERVER Instance "db9", status READY, has 1 handler(s) for this service... Handler(s): "DEDICATED" established:1 refused:0 state:ready LOCAL SERVERThe command completed successfullyWhat the Listener determines the service name to be (which I’ve highlighted in bold) iswhat should go into this screen as the service name. When you’ve entered a name, press[Next].Copyright © Howard Rogers 2002 3/17/2002 Page 4 of 14
  • 5. Creating a tnsnames.ora file Networking TipsHere we need to specify which networking protocol to use for connections to the just-specified Instance. You’ve a choice, as you can see… but what choices here dependsentirely what networking protocol adapters have been installed beforehand. See my paper“What does "Protocol Adapter Not Found" mean?” for details about these. I suspect thatthe majority of Users are going to be using TCP/IP for their connections, and that’s the oneI’ve selected here. One interesting note: in 9i, IPX/SPX is no longer a supported networkprotocol. Choose your protocol, and click [Next].Now you have to know a little about how your Listener has been configured –in other words,you can’t really create a tnsnames.ora until after you’ve configured your Listener. Twopieces of information are required: what box does the Listener reside on, and what port isit listening on.In this example, I’ve used a machine name for the ‘Host Name’ field. That rather assumesthat I have an external mechanism for resolving that name, such as an lmhosts file, orsome sort of Directory Service. Actually, I use Windows 2000 Active Directory, so thisentry makes sense. In the absence of those sorts of mechanisms, typing in the IP addressof the machine directly would have been appropriate.The default port for any Listener is 1521 (from dim and distant memory, it used to be 1526on Oracle 7). Automatic instance registration is a doddle when the default port is used aspart of Listener configuration, but gets rather more complicated if any other port isselected (see my paper “What is automatic instance registration, and is it useful?” fordetails). Unless there are particular constraints on your freedom of action, therefore, I’dalways recommend using the default port. In which case, you can now just click [Next],because the wizard by default selects for that port. Of course, if you’ve previouslyCopyright © Howard Rogers 2002 3/17/2002 Page 5 of 14
  • 6. Creating a tnsnames.ora file Networking Tipsconfigured the Listener to listen on a non-default port, you’ll need to click the ‘Useanother port number” radio button, type in the port number, and then click [Next].And that’s it really. All you’ve done is to specify which Instance to connect to, whatprotocol to use for connections to that Instance, and given the location details for theListener that is handling connection requests for that Instance. The rest of the wizard ismerely designed to make sure that all the information you’ve provided is accurate.I strongly suggest you select the ‘Yes, perform a test’ option, and then click [Next]. You’llget one of two sorts of responses. The bad sort will look like something like this:Copyright © Howard Rogers 2002 3/17/2002 Page 6 of 14
  • 7. Creating a tnsnames.ora file Networking TipsIn this particular case, there’s obviously a problem with the service name I supplied 4screens ago. Usually, that’s because the supplied service name doesn’t match the globaldatabase name under which the Instance has registered itself with the Listener. If that’syour problem, just click [Back] as many times as it takes to get to the relevant earlierscreen, and correct your problem. In my case, going back and changing the service namefrom “db9” to “db9.aldeburgh.local” (which, you’ll remember, is what the Listener knowsmy service name as –see the lsnrctl output on page 4), and then clicking [Next] to get backto the testing screen yields this response, second time around:This still doesn’t look too good, but if you read the error message carefully, it’s clear thatin fact connectivity to the Instance has been established. The problem this time is thatthe test uses (by default) the username “SCOTT” and the password “TIGER”. If yourdatabase doesn’t have a user of that name, or if you’ve changed Scott’s password, thenthe “invalid username/password; logon denied” error message is rather expected. Thepoint, though, is that the wizard must have been able to contact that database to find outthat no such User account exists. All we really need to do to make sure is to get thewizard to try connecting as a User who we can guarantee exists in the database –and aprime candidate for that would be SYSTEM, password MANAGER. To change the test’slogon credentials, just click the [Change Login] button:Copyright © Howard Rogers 2002 3/17/2002 Page 7 of 14
  • 8. Creating a tnsnames.ora file Networking TipsSupply the new username and password (as I’ve done here), and then click [OK].Immediately you do that, the wizard makes a fresh attempt to logon to the database, andyou should see a screen like this:Once you know that the logon works, you can click [Next]. You’ll then see this screen:Here, you supply a “Net Service Name”. This has nothing necessarily to do with the‘Service Name’ we supplied back on Page 3, but can be any friendly name you want to useto connect to the database. The fact that your database is technically known by theListener as, for example, “db9.aldeburgh.local” doesn’t stop you from naming it here asCopyright © Howard Rogers 2002 3/17/2002 Page 8 of 14
  • 9. Creating a tnsnames.ora file Networking Tipssomething rather more intuitive, such as “SALES”, or “ACCOUNTS” or “CUSTOMERS”. Thename you supply here is what Users will supply when making connections, so it helps if it’ssomething meaningful and obvious. The screen will usually supply a default name,extracted from the full service name entered earlier, but feel free to over-type thesuggestion with anything that makes sense to you.Finally, click [Next], and you’ll see this screen:If you want to go through the entire process to establish other connections to the same ordifferent databases, select [Yes], and click [Next]. Otherwise, make sure [No] is selected,click [Next], and you’ll get a confirmation message that “Net service name configuration iscomplete”. One more click of the [Next] button, and you’ll be back to the first screen ofthe wizard. From there, you can just click [Finish] –whereupon the wizard will close.At this point, I’d recommend making sure that connectivity really has been established.The easiest way to do that would be to fire up SQL*Plus at the command line, and see whathappens when you try and establish a connection. Here’s what happens when I try that:C:Documents and Settingshowardjr>sqlplus /nologSQL*Plus: Release 9.0.1.0.1 - Production on Sun Mar 17 09:30:37 2002(c) Copyright 2001 Oracle Corporation. All rights reserved.SQL> connect system/manager@salesERROR:ORA-12154: TNS:could not resolve service nameCopyright © Howard Rogers 2002 3/17/2002 Page 9 of 14
  • 10. Creating a tnsnames.ora file Networking TipsClearly all is not well with this connection, even though the wizard seemed happy enough.So at this point, we need to look at the tnsnames.ora file that the wizard created for us,and see what on Earth is going on.All Oracle networking configuration files are, by default, stored in theORACLE_HOME/network/admin directory on Unix, and ORACLE_HOMEnetworkadmin directory on Windows(and obviously, “ORACLE_HOME” there is an environment variable that points to whateverparent directory you’ve already established as the home for your database files). You canchange the default location, incidentally, by setting yet another environment variablecalled TNS_ADMIN. So, this command means I can move my configuration files to the rootof the C: drive: set TNS_ADMIN=C: (on Unix, you use the “export” command, ratherthan “set”, but otherwise it’s much the same).So, if we go to the networkadmin directory (or wherever TNS_ADMIN is pointing), weshould find our tnsnames.ora file, which we can open in the text editor of our choice.Mine looks like this:# TNSNAMES.ORA Network Configuration File:F:oracleora90networkadmintnsnames.ora# Generated by Oracle configuration tools.SALES.ALDEBURGH.LOCAL = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local) ) )Here, the connection problem I had before is perfectly obvious: I was trying to connect tosomething called “SALES”, and the tnsnames.ora only knows something about an Instancecalled “SALES.ALDEBURGH.LOCAL”. Hence the “could not resolve service name” errormessage I was receiving earlier. It means that the name you supplied after the “@”symbol doesn’t match any of the tns aliases (that is, the friendly names used to identify adatabase) that exist in the tnsnames.ora file.If I go back to SQL*Plus armed with this knowledge, and try again using the correct alias, Iget this:SQL> connect system/manager@sales.aldeburgh.localConnected.Now this is all very well, but it’s not what we wanted. We wanted our Users to be able totype ‘@SALES’ and have the connection work. Having to type all the rest of the long-winded domain name is, frankly, a pain in the neck.Copyright © Howard Rogers 2002 3/17/2002 Page 10 of 14
  • 11. Creating a tnsnames.ora file Networking TipsThere are two approaches to tidying this up. We can either edit the tnsnames.ora filedirectly, so that the tns alias simply reads “SALES”. Or we can get Oracle to automaticallyappend the domain name (in my case, ‘aldeburgh.local’) to any alias the User supplies,every time they supply it.For the first approach, you need simply edit the tnsnames.ora so that it reads like this:# TNSNAMES.ORA Network Configuration File:F:oracleora90networkadmintnsnames.ora# Generated by Oracle configuration tools.SALES = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local) ) )Notice it’s just that first line that gets altered –the details of the SERVICE_NAME, forexample, remain untouched. Save that, and then back in SQL*Plus, we can try again:SQL> connect system/manager@salesConnected.So that’s nice and easy.The more ‘technically correct’ approach is to configure a sqlnet.ora file that reads like this:# SQLNET.ORA Network Configuration File: F:oracleora90networkadminsqlnet.ora# Generated by Oracle configuration tools.NAMES.DEFAULT_DOMAIN = aldeburgh.localNAMES.DIRECTORY_PATH= (TNSNAMES)The first line of this file tells Oracle to always assume that references to “SALES” on itsown should actually be interpreted as referring to SALES.aldeburgh.local. In other words,Oracle will automatically append the specified domain name on to the end of a connectionalias, if it is needed.So if our tnsnames.ora file still reads:SALES.ALDEBURGH.LOCAL = (DESCRIPTION =…etc, then with a sqlnet.ora looking like the one I’ve just shown you sitting in theORACLE_HOMEnetworkadmin directory, we can go back to SQL*Plus and do this:Copyright © Howard Rogers 2002 3/17/2002 Page 11 of 14
  • 12. Creating a tnsnames.ora file Networking TipsSQL> connect system/manager@SALESConnected.So now our Users can connect with the short form alias, even though the tnsnames.ora stillcontains the long form alias. On the other hand, if you try this:SQL> connect system/manager@sales.aldeburgh.localConnected.…then it’s clear that Oracle is smart enough to notice that you’ve been good enough tosupply the domain name yourself, and it won’t append the default domain name.Just to summarise that: SALES = SALES.ALDEBURGH.LOCAL = (DESCRIPTION = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = (ADDRESS = (PROTOCOL = TCP)(HOSTIf your tnsnames TCP)(HOST = mozart)(PORT = 1521)) = mozart)(PORT = 1521)) ) )reads like this: (CONNECT_DATA = (CONNECT_DATA = (SERVICE_NAME = (SERVICE_NAME = db9.aldeburgh.local) db9.aldeburgh.local) ) ) ) )And your NAMES.DEFAULT_DOMAIN = aldeburgh.localsqlnet.ora reads Empty, or simply doesn’t exist NAMES.DIRECTORY_PATH= (TNSNAMES)like this: Connect system/manager@salesThen this ANDconnection will Connect system/manager@saleswork: Connect system/manager@sales.aldeburgh.local ConnectBut this one won’t: Nothing: everything works! system/manager@sales.aldeburgh.localBecause using the sqlnet.ora file to supply a default domain gives you the flexibility ofbeing able to use both connection strings, the Oracle recommended approach is to use thatmethod to sort out the connection problem. (Incidentally, as my paper “What doessqlnet.ora do for me?” explains, the sqlnet.ora has many more uses than just this one, sothere are other reasons for this being the appropriate solution).On the other hand, I’ll confess that, because… • I run my network with TCP/IP (the default protocol) • my Listener always gets given a default name and a default port • I use local naming methods (that is, a tnsnames.ora) • I don’t need Windows account authentication to allow access to the database…I actually have no need for a sqlnet.ora, and therefore rarely bother to create one. So Iwould myself resort to simply making a direct edit of the tnsnames.ora file to get a quickfix to the problem.Copyright © Howard Rogers 2002 3/17/2002 Page 12 of 14
  • 13. Creating a tnsnames.ora file Networking TipsThe point I think I want to make in conclusion is that the Net Configuration wizard is onlythe start of the exercise. It makes the creation of a tnsnames.ora file very easy, but itmay end up introducing certain elements into the file which continue to cause you (or yourUsers grief). Remembering that at the end of the day it’s only a text file, you can alwaysinvoke any old text editor to knock it into a shape that suits you.Just remember that, when you do choose to edit the file directly, you need to be carefulnot to disturb the formal syntax or layout too much.For example, this tnsnames.ora won’t work:SALES =(DESCRIPTION =(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521)))(CONNECT_DATA =(SERVICE_NAME = db9.aldeburgh.local)))Here, I’ve stripped out all the careful indenting that the wizard supplied (and that’s theonly change I’ve made), and when I try to connect, I get this:SQL> connect system/manager@SALESERROR:ORA-12154: TNS:could not resolve service nameIt’s really not so much that it can’t resolve the service name (after all, the tns alias is“SALES”, and that’s what I’ve supplied in the connect string) as that it can’t parse thetnsnames.ora file in the first place.This tnsnames.ora, however, will work:SALES = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local)) )Even this one works:SALES = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local)))Here, I’ve retained the indentations of the lines, but I’ve combined several lines into one.Just to emphasise how sensitive the thing can be, I’ll try that again, using exactly the samelayout as before, but with just a couple of “minor” changes:Copyright © Howard Rogers 2002 3/17/2002 Page 13 of 14
  • 14. Creating a tnsnames.ora file Networking TipsSALES =(DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521)))(CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local)))… once again, the only difference here is that there are no indents to the lines.And one last test, just to show you how confusing and frustrating this can be:SALES =(DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = mozart)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = db9.aldeburgh.local)))That last one works, though you’ll be hard-pressed to spot the difference between it andthe earlier one that didn’t. In fact it is the existence of a single space before the“(CONNECT_DATA…” line!The message is simple, therefore: Spaces and indentation are significant (that’s whyusing the wizard in the first place, which gets all the layout correct, is stronglyrecommended).Copyright © Howard Rogers 2002 3/17/2002 Page 14 of 14