As far as I know, the jury is still out - I haven't had a chance yet to see
if (a) the problems Dan found in 9.0.1.1 are fixed and (2) I like the way it
works. Also, it does require 9i and I'm not yet ready to go there with
everything. Even with 9i and system managed undo, rule #4 will still be in
effect!
Don Granaman
[certifiable OraSaurus]
- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
Sent: Saturday, June 29, 2002 9:38 PM
Don,
9i has system managed undo -- you don't think it works yet?
Rachel
- Don Granaman <granaman_at_cox.net> wrote:
> I prefer to have OPTIMAL set and deal with "long running large
> transactions"
> another way - setting "OPTIMAL" on the developers! Granted, this
> doesn't
> work for 3rd party products, but I usually deal with in-house
> applications.
> Getting this to work requires: (1) having enough rollback segments,
> (2)
> large enough rollback segments that extends almost never occur, and
> (3) NOT
> having the "one giant rollback segment for large jobs", and, most
> importantly, (4) all "batch-lookin' thingies" have to be reviewed by
> the DBA
> and optimized, by either the DBA or the developer - or both, until
> they pass
> muster. Using this, I rarely seen an ORA-01555 or a rollback shrink
> (over
> six months on the systems I'm working with now) - and when I do, I
> know that
> it (usually) means that somebody broke rule #(4). When that happens,
> I
> track it down and work with the developer to fix it. My experience
> is that
> the vast majority of developers are receptive - they actually like to
> have
> their code run without problems.
>
> Of course, this assumes that the "wasted" disk space for (1) and (2)
> is not
> a significant issue. It rarely is, but I work almost exclusively
> with
> (essentially) OLTP systems where space is typically less critical
> than I/O
> throughput capability and reliability. Usually, we have to add disks
> for
> performance rather than space. The database datafile drives are
> typically
> 36 GB (less often 18 GB) and are rarely "full", so a GB or two more
> for
> rollback tablespace is OK. If I had to operate under the space
> constraints
> that many seem to have, I might not set OPTIMAL either.
>
> I am looking forward to the day that this "no OPTIMAL" suggestion
> fades into
> the "myths and folklore" category. Either because of basic policy
> changes
> (e.g. the extents myth), a better Oracle algorithm (e.g. 10i system
> managed
> undo???), more intelligently designed batch processes in
> applications, or
> the trend towards ever-increasing drive size.
>
> Note: All this doesn't mean that I don't understand why so many use
> the
> "manual shrink" method. My philosophy differs in that not setting
> OPTIMAL
> should be a last resort, not a blanket policy.
>
> Don Granaman
> [OraSaurus]
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Thursday, June 27, 2002 10:13 AM
>
>
> One of the constant comments regarding rollback segments is not to
> set
> optimal. I am wondering why this setting is often discouraged. I have
> my own
> ideas, but I want to gather more opinions and experiences.
>
> Daniel W. Fink
> Sr. Oracle DBA
> MICROMEDEX
> 303.486.6456
>
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Don Granaman
> INET: granaman_at_cox.net
>
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Received on Sun Jun 30 2002 - 21:38:19 CDT
