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Re: Indexing TNSNAMES?

From: Sybrand Bakker <oradba_at_sybrandb.demon.nl>
Date: Tue, 13 Nov 2001 16:23:17 +0100
Message-ID: <ede2vtcotupodb6sema2ns4in07mls1mdg@4ax.com>


On Tue, 13 Nov 2001 14:16:08 GMT, Ed_Stevens_at_nospam.noway.nohow (Ed Stevens) wrote:

>A few days ago I posted a question here (see "Puzzling Results of
>Using Bequeaqth") that didn't draw any responses, so I posted it to
>MetaLink. (I generally find this NG provides faster response and
>better advice than MetaLink). Their response was to point me to a
>white paper -- CR 212951 --that didn't even approach the subject of my
>question, but did have a couple of statements I found interesting:
>
>"When a client application initiates a transaction to retrieve data
>from a server, the entire Tnsnames.ora file is read."
>
>"Instead of reading the entire file and scanning for the relevant
>entry, it is better to implement an indexing method."
>
>First, while I had never been told otherwise, I always assumed
>tnsnames was read until the relevant entry was found, rather than
>reading the entire file into a buffer then scanning. Right or wrong?
>
>Second, and much more interesting . . . I've never heard of indexing
>tnsnames. What is this all about?
>
>BTW, I'm still searching for an answer to my question in "puzzling
>performance results with bequeath connection" if anyone wants to take
>a crack at it.
>
>Thanks.
>
>- Ed Stevens

The _entire_ file is definitely read. You can easily see that with trace_level_client = 16.
One of the consequences is (I once run into this, and maybe I would better post it):
if you have a tnsnames.ora with syntax errors, sqlplus or whatever won't just bail out, it simply doesn't construct a proper tnsnames.ora in memory. Guess what is the result:
ORA-12154, failed to resolve service name for _all_ your service names.

I'm not too sure about the second assertion. However I do often find querying a names server is faster than processing tnsnames.ora

Hth

Sybrand Bakker, Senior Oracle DBA

To reply remove -verwijderdit from my e-mail address Received on Tue Nov 13 2001 - 09:23:17 CST

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