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Disabling Sybase Logging

3 posts in Windows NT Last posting was on 2000-10-23 08:39:57.0Z
Anonymous Posted on 2000-10-20 07:04:40.0Z
From: Anonymous@sybase.com
Date: Fri, 20 Oct 2000 03:04:40 -0400
Newsgroups: sybase.public.sqlserver.nt
Subject: Disabling Sybase Logging
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Article PK: 1089034

Hi all:

My production environment consists of Sybase 11.9.2 (in the next future
will be mograted to 12.0) running on NT 4.0. The database is pretty large
(200 Gb) and consists of tables loaded from the input stream generated by
telco switches.

So no user ever issues INSERT, UPDATE, DELETE. Is there any way to disable
logging? We are wasting a lot of time in the phase of data loading because
the program that reads telco input and insert it into tables must wait for
the transaction log to be written.

Thanks for your cooperation.

Stefan Giuros
stefan.giuros@connex.ro


"Mark A. Parsons" <pegasys Posted on 2000-10-20 17:38:10.0Z
Message-ID: <39F08302.6EACD332@_internet.co.nz>
Date: Sat, 21 Oct 2000 06:38:10 +1300
From: "Mark A. Parsons" <pegasys@_internet.co.nz>
Organization: Pegasys (2000) Limited
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Subject: Re: Disabling Sybase Logging
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> So no user ever issues INSERT, UPDATE, DELETE.

Logging is in place to insure transactional consistency during the
insert/update/delete (in case of a 'failure'), to insure recovery if/when the
dataserver 'crashes', to defer the io writes to data and index pages, etc.

> Is there any way to disable logging?

No.

Yeah, yeah, yeah ... there is supposedly a trace flag floating around which
will disable logging, however, this flag is *NOT* supported by Sybase (it's
used for internal Sybase engineering and TS testing *only*). This trace flag
is also known to cause corruption ... not something I believe you want in a
200GB production database?

> We are wasting a lot of time in the phase of data loading because
> the program that reads telco input and insert it into tables must wait for
> the transaction log to be written.

Wasting a lot of time? Without a log you would *waste* even more time while
the individual data and index pages are inserted/updated. Without a log you
would waste a lot of time trying to recreate 'lost' transactions that weren't
written to disk *when* the dataserver goes down (ie, crashes).

If you don't need the 'waste' of a log ... why use Sybase (or any other
RDBMS)? If all you want is a place to dump some data I'd suggest you just put
the data into files that your application can index/search on ... would be a
lot less expensive than an RDBMS *and* you could get rid of all that wasted
logging. <g>

------------------

If you're having problems/delays in getting your data into the database I'd
suggest you look at your database structure, disk layouts, how you're loading
the data, etc ... and weigh this against your performance requirements,
recovery requirements, whether or not you can replace this 200GB if you should
happen to lose some/all of it, etc.

Have you looked at using striped disks or a 'guaranteed writes' disk caching
system? Are you batching your inserts inside transactions so as to defer log
writes (this can generate a *huge* improvement, ie, decrease, in log io
times)? What about partitioning your data ... either at the table/partition
level, separate table level, or database level? How many indices do these
tables have and are all of them really necessary? Does sp_sysmon show any
places where your dataserver could be tuned for better performance? If you're
using something like bcp ... have you optimized this process to cut down on
network delays (eg, load from the dataserver's host box), or speed up network
transfers (eg, increased packet size)?


--
Mark A. Parsons

Iron Horse, Inc. iron_horse@compuserve.com
Pegasys (2000), Ltd pegasys@internet.co.nz


Anonymous Posted on 2000-10-23 08:39:57.0Z
From: Anonymous@sybase.com
Date: Mon, 23 Oct 2000 04:39:57 -0400
Newsgroups: sybase.public.sqlserver.nt
Subject: Re: Disabling Sybase Logging
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Article PK: 854787

Dear Mark:

I'm afraid i exposed my problem quite uncomplete. The system works
something like this:
(1) Telco switches generates a lot of files containing call data records,
in ASN-1 format;
(2) These files are generated on a system called 'mediation server' who is
about five miles away. No way to put the dataserver on the same mediation
server and network is not a bottleneck.
(3) Once a day, a program is launched. It reads input files, convert them
and sends result into the Sybase machine, using bcp-functions of the
CT-lib.
(4) After this phase is finished, all we do, all day long, is to run
various queries against this database.. you know, the type of stuff that
management guys seem to be happy to looking at: number and calls duration
versus destination, profiles, switch loading, calls versus time of day...
That's why we must use a RDBMS instead of a collection of flat files,
indexed or not.
(5) There are many indexes, that's true, because the management is not
happy to wait more that 2.5 miliseconds for a report (and this time is
increased at 3 miliseconds only then you say that you have to compose the
query..:-))
(6) Data is split over a hardware RAID-5 subsystem. Disks are SCSI Ultra
Wide, 10k RPM.
(7) Maybe some data is not useful, but (alas) who knows what new reports
should be generated? and what data should they need?

So you see that most of your ideas have been already applied. And i do
remember that in Oracle there is a clause NO LOG and i just expected that
someone knows an (safely) equivalent of this.

But of course I appreciate your suggestions and your answer.

Sincerey, yours
Stefan Giuros
stefan.giuros@connex.ro