RE: Question about db links and tnsnames.ora
- From: "Hollis, Les" <Les.Hollis@xxxxxx>
- To: <tomday2@xxxxxxxxx>, <Oracle-L@xxxxxxxxxxxxx>
- Date: Sat, 26 Feb 2005 09:53:28 -0600
One of the best books I've come across for networking is Oracle 8i
Networking 101 by Marlene Theriault ISBN 0072125179
Haven't looked for but she probably has an updated version.
I used this book to setup my Oracle Names environment and all I need
when I create a DB LINLK is the tnsnames alias in Onames.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Thomas Day
Sent: Friday, February 25, 2005 6:20 PM
To: Oracle-L@xxxxxxxxxxxxx
Subject: Re: Question about db links and tnsnames.ora
Can anyone recommend a good book (or even an article) on how to
configure a tnsnames entry and what the corresponding sqlnet.ora
should contain?
I've been through the manuals and I think that I have a handle on it
but I've never had the slightest bit of Oracle training on the
subject.
What I've seen is that many (if not most) DBAs copy an existing entry
and edit it with the new sid, port, and ip address.
At a recent job we had a snapshot database with a database link to one
side of a RAC cluster. If that side went down the refreshes would
fail and my predecessor would drop the database link and recreate it
pointing to the working side of the RAC. I finally figured out how to
make the link with automatic failover but I couldn't find any good
documentation, especially one with an example.
create database link failover connect to scott identified by tiger using
'(DESCRIPTION_LIST=3D(DESCRIPTION=3D(ADDRESS_LIST=3D(ADDRESS=3D
(PROTOCOL=3DTCP)(HOST=3Dxx.xx.xx.x1)(PORT=3D15xx)))
(CONNECT_DATA=3D(SID=3Dside1)(failover_mode=3D(type=3DSESSION)(method=3DB=
ASIC))))
(DESCRIPTION=3D(ADDRESS_LIST=3D(ADDRESS=3D(PROTOCOL=3DTCP)(HOST=3Dxx.xx.x=
x.x2)
(PORT=3D15xx)))(CONNECT_DATA=3D(SID=3Dside2)(failover_mode=3D
(type=3DSESSION)(method=3DBASIC)))))'
There is a limit to how long the "using" token can be. This
approaches it. I usually don't have spaces or carrige returns but
I've formatted this a little for readability.
I am serious about wanting to find out why this works. It does, but I
think that I got lucky and picked the right set of parameters. Is
there a white paper, perhaps, that explains what goes with what and
what the entries in sqlnet.ora would be? Ditto for the entries in
listener.ora. I've set up automatic failover on a listener as well
but again it was a lot more hard work than I think it should be.
I haven't found OEM generated entries to be completely satisfactory.=20
Too often they don't work or, if they do, then some other entry
doesn't. Personally I find this to be one of the least documented
aspects of a DBA's work. Have I just been looking in all the wrong
places?
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