RE: SQL High version count because of too many varchar2 columns
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <usn@xxxxxxxxx>, <eagle.f@xxxxxxxxx>
- Date: Wed, 12 Sep 2012 08:49:55 -0400
Notice that the cpu cost of version control may vary significantly from
language to language and amongst different techniques.
Initializing the bind var from a constant *may* be a single memcpy depending
on the language implementation, then replacing the front end of the buffer
with the actual value *may* also be a single memcpy. Your mileage may vary.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Martin Klier
Sent: Wednesday, September 12, 2012 3:57 AM
To: eagle.f@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: SQL High version count because of too many varchar2 columns
Hi Eagle Fan,
this is a known issue. All solutions I know are an application approach:
Avoid this length changes of the bind variables, or pad them with blanks.
The last one is ugly or useless, but that's all you can do.
"Technical background: The database does adjust the length of CHAR bind
buffers to preset sizes. There are four steps: 32, 128, 2000 and 4000 bytes.
So if we are execute a statement with a bind value of 10 bytes, the buffer
will be 32 bytes. Do we re-execute it with 52 bytes in the bind variable,
the previously created child cursor cannot be reused, and will be recreated
with a bind buffer of 128 bytes. The system view v$sql_shared_cursor
indicates this invalidated child cursor as BIND_LENGTH_UPGRADEABLE."
I've been speaking about this problem and the impacts of many SQL versions
at IOUG 2012 and nobody in the audience had a better solution, I'm afraid.
If you are interested in the presentation or paper, have a look here:
http://www.usn-it.de/index.php/2012/04/26/ioug-2012-presentation-resolving-c
hild-cursor-issues-resulting-in-mutex-waits/
If you have further questions, just answer here.
Best regards
Martin
Eagle Fan schrieb:
> Hi:
> We have a table which has 17 varchar2 columns. Each varchar2 column
> has different bind variable ranges.
>
> for example varchar2(4000) has 4 ranges:
> 0-32,33-128,129-2000,2001-4001. if the bind variables' length is in
> different ranges, it will create a new version!
>
> With 17 varchar2 columns, we have more than 3000 versions!
>
> We are using java code, if there any method to make oracle bind all
> different variables with the max length?
>
> Thanks.
>
>
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