How to open oracle listner for three database instances

Question

please help me with following questions
I have 3 database instances
orcl
JIP02T
JIP04T
when i start the oracle database, does it start all 3 instances? when i start the oracle listner, does it start listner for all 3 instances?
when i echo $ORACLE_SID
[ora112@localhost admin]$ echo $ORACLE_SID
orcl
i can only see orcl and oracle listner is started only for one database instance.i can connect to only one database instance usign sql developer how can i start oracle database listner for other database instances as well

Answer 1

ShishirTekadeR wrote:
. oraenv
Note that is "dot" SPACE oraenv
You will be prompted for the value of ORACLE_SID (one of the databases). It looks like this:
oracle:orcl$ . oraenv
ORACLE_SID = [orcl] ? dwsbx
The Oracle base for ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1 is /u01/app/oracle
oracle:dwsbx$
HIGHLY APPRECIATED U R IMP Tips!!!!!
But it’s very difficult to remember & manually enter oracle SID & HOME details every time after run (. Oraenv)
.profile creation is simple method and no need to remember SID & HOME details.(for multiple DB in one server)You don't have to "remember & manually enter oracle SID & HOME details every time after run " oraenv sets all those details for you. All you have to remember is the name of the instance you want to work with. The same thing you'd have to remember if you if you created (as you suggested) three different "profiles" - actually three different shell scripts, each to set the environment for a specific instance.
Yes, I do place "default" settings in .bash_profile. But with multiple databases the "default" settings are often not going to be what you need so you'll still have to run some process to change them. Either a home-grown script or oraenv. And either way you will have to remember the names of the instances you have to chose from. So in general I see no advantage of reinventing the wheel.
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As per user information
He is using different port number for different instanceWhich accomplishes absolutely nothing except extra configuration headaches. It accomplishes nothing for security. It accomplishes nothing for availability.
And also it is very simple method to manage three different DB in three different listener entry (for DB maintenance activity.)Not as easy as managing one default listener. By far the most frequent listener configuration issue I see on this forum is when people try to configure one listener per database.
Single listener in multiple instance (if listener down all DB connection will affect)And why would the listener be down? I've been working full time with Oracle since version 7.3 - somewhere around 1995. I've NEVER seen a listener fall over and die. I have seen many people on this forum whose db connections failed because they were trying (unsucessfully) to configure multiple listeners.
All of my servers are running multiple databases. I have one test server that is running close to a dozen separate databases. One listener. I've NEVER had a situation where I thought to myself, "Gee, it would really help if I had created a separate server for each database"
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Best Regards,
Shishir Tekade.
My Blog: http://shishirtekade.blogspot.com
Edited by: ShishirTekadeR on Dec 27, 2012 10:29 PM
Edited by: ShishirTekadeR on Dec 27, 2012 10:30 PM
Edited by: ShishirTekadeR on Dec 27, 2012 10:31 PM