Sybase NNTP forums - End Of Life (EOL)

The NNTP forums from Sybase - forums.sybase.com - are now closed.

All new questions should be directed to the appropriate forum at the SAP Community Network (SCN).

Individual products have links to the respective forums on SCN, or you can go to SCN and search for your product in the search box (upper right corner) to find your specific developer center.

Memory allocation page

3 posts in General Discussion Last posting was on 2011-08-20 07:06:00.0Z
sybanva Posted on 2011-08-09 13:48:15.0Z
Sender: 6ba4.4e41398b.1804289383@sybase.com
From: sybanva
Newsgroups: sybase.public.ase.general
Subject: Memory allocation page
X-Mailer: WebNews to Mail Gateway v1.1t
Message-ID: <4e413a9f.6c02.1681692777@sybase.com>
NNTP-Posting-Host: 10.22.241.41
X-Original-NNTP-Posting-Host: 10.22.241.41
Date: 9 Aug 2011 06:48:15 -0700
X-Trace: forums-1-dub 1312897695 10.22.241.41 (9 Aug 2011 06:48:15 -0700)
X-Original-Trace: 9 Aug 2011 06:48:15 -0700, 10.22.241.41
Lines: 14
Path: forums-1-dub!not-for-mail
Xref: forums-1-dub sybase.public.ase.general:30459
Article PK: 72637

All,

Is memory allocation page size as per below
sybook note, same as @@pagesize global variable ?

Secondthing , Is ASE using @@pagesize (i.e. 2k) for logical
i/o and @@maxpagesize for physical i/o? I had little
confusion for the same.

The logical page size is not the same as the memory
allocation page size. Memory allocation page size is always
2K, regardless of logical page size, which can be 2, 4, 8,
or 16K. Most memory-related configuration parameters use
units of 2K for their memory page size.


sybanva Posted on 2011-08-20 04:16:30.0Z
Sender: 6669.4e4dd353.1804289383@sybase.com
From: sybanva
Newsgroups: sybase.public.ase.general
Subject: Re: Memory allocation page
X-Mailer: WebNews to Mail Gateway v1.1t
Message-ID: <4e4f351e.b5f.1681692777@sybase.com>
References: <4e413a9f.6c02.1681692777@sybase.com>
NNTP-Posting-Host: 10.22.241.41
X-Original-NNTP-Posting-Host: 10.22.241.41
Date: 19 Aug 2011 21:16:30 -0700
X-Trace: forums-1-dub 1313813790 10.22.241.41 (19 Aug 2011 21:16:30 -0700)
X-Original-Trace: 19 Aug 2011 21:16:30 -0700, 10.22.241.41
Lines: 29
Path: forums-1-dub!not-for-mail
Xref: forums-1-dub sybase.public.ase.general:30482
Article PK: 72661

All,
Again gone through the doc, but still same confusion, will
appriciate any help this regard.

Suppose logical page size is 8k then physical io would be
done on 8k size, what about logical io? Where we can fit
memory allocation pages thats always 2k.

l i/o p i/o
ASE exe <----> Data cache <---> Device
? 4k Size 4k size i/o
buffer

> All,
>
> Is memory allocation page size as per below
> sybook note, same as @@pagesize global variable ?
>
> Secondthing , Is ASE using @@pagesize (i.e. 2k) for
> logical i/o and @@maxpagesize for physical i/o? I had
> little confusion for the same.
>
> The logical page size is not the same as the memory
> allocation page size. Memory allocation page size is
> always 2K, regardless of logical page size, which can be 2
> , 4, 8, or 16K. Most memory-related configuration
> parameters use units of 2K for their memory page size.


Rob V Posted on 2011-08-20 07:06:00.0Z
From: Rob V <rob@DO.NOT.SPAM.sypron.nl.REMOVE.THIS.DECOY>
Reply-To: rob@DO.NOT.SPAM.sypron.nl.REMOVE.THIS.DECOY
Organization: Sypron BV
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:6.0) Gecko/20110812 Thunderbird/6.0
MIME-Version: 1.0
Newsgroups: sybase.public.ase.general
Subject: Re: Memory allocation page
References: <4e413a9f.6c02.1681692777@sybase.com> <4e4f351e.b5f.1681692777@sybase.com>
In-Reply-To: <4e4f351e.b5f.1681692777@sybase.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
NNTP-Posting-Host: vip152.sybase.com
X-Original-NNTP-Posting-Host: vip152.sybase.com
Message-ID: <4e4f5cd8$1@forums-1-dub>
Date: 20 Aug 2011 00:06:00 -0700
X-Trace: forums-1-dub 1313823960 10.22.241.152 (20 Aug 2011 00:06:00 -0700)
X-Original-Trace: 20 Aug 2011 00:06:00 -0700, vip152.sybase.com
Lines: 76
Path: forums-1-dub!not-for-mail
Xref: forums-1-dub sybase.public.ase.general:30483
Article PK: 72662


On 20-Aug-2011 06:16, sybanva wrote:
> All,
> Again gone through the doc, but still same confusion, will
> appriciate any help this regard.
>
> Suppose logical page size is 8k then physical io would be
> done on 8k size, what about logical io? Where we can fit
> memory allocation pages thats always 2k.
>
> l i/o p i/o
> ASE exe<----> Data cache<---> Device
> ? 4k Size 4k size i/o
> buffer
>
>
>
>> All,
>>
>> Is memory allocation page size as per below
>> sybook note, same as @@pagesize global variable ?
>>
>> Secondthing , Is ASE using @@pagesize (i.e. 2k) for
>> logical i/o and @@maxpagesize for physical i/o? I had
>> little confusion for the same.
>>
>> The logical page size is not the same as the memory
>> allocation page size. Memory allocation page size is
>> always 2K, regardless of logical page size, which can be 2
>> , 4, 8, or 16K. Most memory-related configuration
>> parameters use units of 2K for their memory page size.

I think you're reading too much into the terminology. 'logical pages'
and 'physical pages' are not regular ASE terminology.
It's simple: an ASE server has a pagesize, indicated by @@maxpagesize.
Forget @@pagesize, it's a remnant of older days.
An ASE server performs logical and physical I/Os of 1 page, i.e. of size
@@maxpagesize. For physical I/Os there are optimizations whereby
sometimes multiple pages are read instead of one. This is referred to as
'large I/O' and typically is an 'extent' of 8 pages (of @@maxpagesize
each). The actual physical I/O size corresponds to the size of the
buffer pool in a data cache. In a data cache, there is always a buffer
pool with @@maxpagesize buffers; you can create additional buffer pools
(with sp_poolconfig) of 2, 4 and 8 times @@maxpagesize.

All of this is unrelated to the 'memory pagesize', which is the unit in
which memory for the procedure cache is allocated. This is always 2KB
regardless of the server pagesize, although some internal optimizations
may sometimes allocate large chunks as well. The fact that @@pagesize
corresponds to this memory pagesize is a coincidence.

The reason the procedure cache 'memory page size' is unrelated to the
'I/O page size' is that pages read from disk are copied into the data
cache. They are not, and never, copied into the procedure cache. The
proccache is used for internal data structures such as query plans (and
many other things), but not for entire datapages.

--

HTH,

Rob V.
-----------------------------------------------------------------
Rob Verschoor

Certified Sybase Professional DBA for ASE 15.0/12.5/12.0/11.5/11.0
and Replication Server 15.0.1/12.5 // TeamSybase

Author of Sybase books (order online at www.sypron.nl/shop):
"Tips, Tricks& Recipes for Sybase ASE" (ASE 15 edition)
"The Complete Sybase ASE Quick Reference Guide"
"The Complete Sybase Replication Server Quick Reference Guide"

rob@NO.SPAM.sypron.nl | www.sypron.nl | Twitter: @rob_verschoor
Sypron B.V., The Netherlands | Chamber of Commerce 27138666
-----------------------------------------------------------------