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Re: service name, sid ..

From: AK <>
Date: Mon, 07 Jul 2003 11:59:43 -0700
Message-ID: <>

Thanks for elaborate information , I really liked it . Still why do u need to provide db name in tnsnames, all one should know is which instance to connect . Instance know , which db to connect . why do net8 bother about dbname ?
----- Original Message -----
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  style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black">From:   Tanel
  href="mailto:[EMAIL PROTECTED]">Multiple recipients of list ORACLE-L   

  Sent: Thursday, July 03, 2003 10:49
  Subject: Re: service name, sid ..   


  There's actually more:

  db_name - identifies database name, has to be the   same what is stated in controlfile (using create database or create   controlfile). You can have several databases with same db_name in one server,   there is no restriction.

  SID - When we actually want to open and use the   database, we have to start an instance which will be servicing the   database. When starting instance, whe have to specify SID (system identifier)   for it. This is actually just a operating system name for instance (or should   I say SGA shared memory segments). As you know, SID is specified using   ORACLE_SID OS environment variable and is only used by listener, when spawning   new processes or when attaching directly to SGA using bequeath protocol.   You can not have instances with same SID in one server, even if you use   different oracle homes.

  instance_name - An Oracle parameter for   specifying Oracle instance name. Seems that operating system doesn't know   anything about it. For example, if you use SID_LIST parameters in your   listener.ora, then listener always knows how to spawn processes for given SID,   because (almost) all it takes to start another server process, is the location   of oracle executable and SID value. But if you want to connect using instance   name (not SID itself) then Oracle instance actually has to register itself   with listener before any server processes can be spawned.   Note that ORACLE_SID and instance_name variables   do not have to match. (Tested on on W2K). If my SID is ORCL for   example and instance_name is TEST, then I can connect using both SID=ORCL and   SID=TEST in CONNECT_DATA section of TNSNAMES (again, the instance name has to   be registered with listener). V$INSTANCE still shows SID (ORCL) in instance   name fielt.

  As we know, in OPS and RAC environment you could   have several instances servicing one database, this is one of common   reasons why db_name and instance_name would be different. (ORCL for db_name,   ORC0, ORC1, ORC2, etc.. for instance names for example). Btw, does anyone know   if I can have the same instance name in all RAC nodes? RAC shouldn't care   much, because it uses instance numbers anyway?

  service_names - this is an additional layer   for logically spreading work across nodes in RAC (and possibly other load   balanced environments such replicated databases and even logical standby). For   example, if you have 4 node RAC and have defined two "services" such OLTP and   REPORTING, then you could assign OLTP for nodes and REPORTING for one, but   during month end reporting you could still keep OLTP on 3 nodes, 1 node purely   for REPORTING and add REPORTING to one or more OLTPs as well. So, when user's   are connecting, they don't request a specific node or instance, they just   request a service. And in load balancing environments then users are directed   to instances, where appropriate service is defined. It gives somewhat   flexibility, but I've never used it myself (thus my explanation here might   wrong ;)

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    href="mailto:[EMAIL PROTECTED]">Multiple recipients of list ORACLE-L     

    Sent: Wednesday, July 02, 2003 9:49     PM
    Subject: service name, sid ..
    <FONT face=Arial

    I am reading oracle network admin guide and     getting confused abt service name, instance name , db name , sid ..     

    why service name is not same as db name .     Earlier service name and sid used to be same thing .. isn't it ( ? )     .
    Can some one clarify with some examples .     

    <FONT face=Arial
size=2>  Received on Mon Jul 07 2003 - 13:59:43 CDT

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