Buffer pool keep and multiple db block sizes

I have a tablespace with 8k block size (database default) and a tablespace with 16k block size. I have db_cache_size and db_16k_cache_size set (obviously).
Also i have buffer cache keep set in the database.
Question: If a table is placed in a tablespace with 16k block size, and it's buffer pool is keep, does it end up in the keep pool (like tables from 8k tablsepace and keep pool set), or it ends in 16k buffer?

You can find in the following online manual
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14220/memory.htm#i16408

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Zfs boot block size and ufs boot block size

Hi,
In Solaris UFS file system , boot block resides in 1 to 15 sectors, and each sector is 512 bytes total makes 7680 bytes
bash-3.2# pwd
/usr/platform/SUNW,SPARC-Enterprise-T5220/lib/fs/ufs
bash-3.2# ls -ltr
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for zfs file system the boot block size is
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Thanks for your reply.
my query is when zfs boot block size is 16K, and on disk 1 to 15 sectors(here boot block going to be installed) make around 8K,
it mean in the 16K,it writes only 8K on the disk
if you don't mid will you please explain me in depth
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http://books.google.co.in/books?id=r_cecYD4AKkC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
please help me to find a doc for kernel bootstrap and initialization for Solaris 10 with zfs and boot archive
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KEEP and RECYCLE buffer pools question...

About the DB buffer cache's two optional buffer pools: KEEP and RECYCLE pools.
If i want a table to be kept in KEEP buffer pool, can i specify that in CREATE TABLE or ALTER TABLE syntax? Or is it possible only at tablespace level?

HI,
You can keep tables at keep pool by specifying storage (buffer_pool keep) parameter.

Buffer data before chart it and block size

I hope you can help me with this situation because I have been stoped in this situation for two days and I think that I won't see the light in the short time and the time is a scarce resource.
I want to use a NI DaqCard-AI-16XE-50 ( 20KS/s accordig to specifications). To acquired data in DasyLab I've been using OPC DA system but when I try get a chart from the signal I get awfull results.
I guess the origin of the problem is the PC is not powerfull to generate a chart in real time, so Is there a block to save the data, then graph the data without use "Write Data" Block to avoid write data to disk?
Another cause of the problem it could be an incorrect set value of Block size, but in my piont of view with the 10Khz, and 4096 of block size is more than neccesary to acquire a signal of 26[Hz] (showing in the photo). If I reduce the block size to 1 the signal showing in the graph is a constant of the first value acquire. Why could be this situation?
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Go to Solution.
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data from DAQcard.PNG ‏95 KB

Is there someone who can help me
I connect CN606TC2 and Dasylab 11... using the RS232 cable, and have done the instruction manual of the book cn606tc2.
In dasylab RS232 module, there is a box:
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Commands requesting data from the scannerCN606TC2)
ASCII [A] hex 41 = Zones/ Alarms/ Scan time
ASCII [M] hex 4D = Model/ Password/ ID#/ # of zones
ASCII [S] hex 53 = Setpoints
ASCII [T] hex 54 = Temperature
I did not understand the program and the ASCII code.
I send [T] in the RS232 monitor and restore dasylab 54.
I am very grateful for your help

MULTIPLE BUFFER POOL의 개념 및 사용 방법 (ORACLE8)

제품 : ORACLE SERVER
작성날짜 : 1999-05-13
Multiple Buffer Pool의 개념 및 사용 방법
1. 필요성
table이나 index 등 segment는 그 사용 빈도나 중요도 등에 따라 memory에
buffering되는 것을 달리 할 필요가 있다. Oracle8에서는 buffer cache에 대해서
multiple buffer pool이라는 새로운 특성의 개념을 제공하여 segment마다 다른
buffer를 사용할 수 있도록 하고 있다.
multiple buffer pool은 'keep', 'recycle', 그리고 'default' buffer pool로
구성되며, 이것을 control하기 위한 internal algorithm은 하나의 buffer pool을
사용할 때와 대부분 마찬가지다. 즉, 기존의 CACHE option이나 full table scan 시
LRU end에 위치시키는 것 등은 모두 변함이 없으며, 단지 그러한 기법들이 각
buffer마다 별도로 적용된다는 것 뿐이다.
2. buffer의 종류
multiple buffer pool의 주요 목적은 서로 다른 형태로 사용되는 것을 나누어 놓
아 서로 방해가 되지 않도록 하는 것으로 정리할 수 있으며, 각각 다음과 같은
경우에 사용하도록 한다.
(1) KEEP buffer pool : 가능한 한 memory에 오랫동안 유지되어져야 하는
segment를 위해 사용되어져야 한다. 자주 사용되어지고 cache size의 약 10%
전후의 크기를 가진 segment가 이 pool을 사용하기에 적당하다.
그러나, 여기에서도 Oracle7.3의 CACHE option과 마찬가지로 새로이 access
되는 segment에 의해 LRU end 쪽으로 이동하는 것이 가능하므로 항상 cache
된다고 보장할 수는 없다.
적당한 크기로 지정하는 것이 중요한데 당연히, 동시에 memory에 올려지기를
바라는 object들의 크기의 합보다는 커야 한다.
(2) RECYCLE buffer pool : 자주 사용되어지지 않거나, buffer pool의 두배보다
큰 정도의 큰 segment가 index search를 하는 작업 등에 사용되어지도록 한다.
(3) DEFAULT buffer pool : 위의 두 buffer pool에 할당되지 않은 나머지는
default buffer pool이 된다. 그러므로 KEEP이나 RECYCLE buffer pool은
없어도 반드시 default buffer pool은 존재하게 된다.
이 buffer pool은 Oracle7의 하나의 buffer pool과 같다.
3. buffer pool을 설정하는 방법
이러한 종류의 buffer pool을 지정하기 위해서 BUFFER_POOL_KEEP과
BUFFER_POOL_RECYCLE이라는 parameter가 존재하며, DB_BLOCK_BUFFERS
와 DB_BLOCK_LRU_LATCHES parameter도 함께 고려하여야 한다.
syntax는 다음과 같다.
BUFFER_POOL_KEEP=(buffers:<value>,lru_latches:<value>) 혹은
BUFFER_POOL_KEEP=<value>
BUFFER_POOL_RECYCLE=(buffers:<value>,lru_latches:<value>) 혹은
BUFFER_POOL_RECYCLE=<value>
위의 syntax에서 보는 바와 같이 각 pool에 대해서 buffer의 갯수 뿐 아니라
LRU latch의 갯수도 지정할 수 있다. 만약 지정하지 않으면 그 pool에 대해서
하나의 latch가 할당되는 것이다.
DEFAULT pool에 대해서는 명시적으로 block의 갯수나 latch의 갯수를 지정할
수 없고, 대신 전체 block의 갯수 (DB_BLOCK_BUFFERS)와 전체 LRU latch의
갯수 (DB_BLOCK_LRU_LATCHES)에서 KEEP과 RECYCLE에 할당된 각각의
값을 뺀 것만큼 default pool에 할당된다.
간단한 예제로 설명하면 다음과 같다.
예를 들어 initSID.ora file에 다음과 같이 parameter가 설정되어 있다고 가정한다.
DB_BLOCK_BUFFERS=1000
DB_BLOCK_LRU_LATCHES=6
BUFFER_POOL_KEEP=(buffers:400,lru_latches:2)
BUFFER_POOL_RECYCLE=100
이러한 경우 KEEP pool에 대해서는 400개의 block과 2개의 LRU latch가 할당
되고 RECYCLE pool에는 100개의 block과 1개의 LRU latch가 할당된다. 그리
고 DEFAULT pool에는 500 (1000-400-100) 개의 block과 3 (6-2-1)개의 LRU latch
가 할당되게 된다.
각 LRU queue에 대해서 block은 균등하게 배분된다.
즉, 이 예에서 DEFAULT queue는 LRU 1번이 167개의 block을 LRU2도 167개, 그리
고 LRU3은 166개의 block을 가지게 되며, KEEP queue는 두개의 latch가 각각
200개씩의 block을 그리고 RECYCLE queue는 100개의 block을 가지게 된다.
이러한 정보는 v$buffer_pool을 통해 확인이 가능하며,
이 예의 경우 다음과 같이 조회된다. 여기에서 set_count가 각 pool에 할당된
latch의 갯수이며, lo_bnum과 hi_bnum이 buffer의 range이다.
SQL> select * from v$buffer_pool;
NAME      LO_SETID HI_SETID SET_COUNT BUFFERS LO_BNUM HI_BNUM
     0 0 0 0 0 0
KEEP 4 5 2 400 0 399
RECYCLE 6 6 1 100 400 499
DEFAULT 1 3 3      500 500 999
각 queue는 최소 50개의 block은 할당받아야 하며, 그렇지 않은 경우에는 오류
가 발생한다. 즉 예를 들어, BUFFER_POOL_KEEP=(buffers:100, lru_latches:3)과
같이 설정하면 alert.log file에 "Incorrect parameter specification for
BUFFER_POOL_KEEP"이라는 오류 메시지가 적히게 되며, 100개의 block에 대해서
최대 두개의 LRU latch만이 가능하게 된다.
4. buffer pool을 지정하는 방법
BUFFER_POOL이라는 Oracle8에서 새로 추가된 storage 절의 parameter를 이용
하여 segment가 사용할 default pool을 지정할 수 있다. segment의 모든 block은
지정된 pool을 사용하게 되며, 아래의 예제와 같이 사용하면 된다.
CREATE TABLE keep_table(t NUMBER(10)) STORAGE (BUFFER_POOL KEEP);
ALTER TABLE recycle_table storage(BUFFER_POOL RECYCLE);
BUFFER_POOL은 tablespace나 rollback segment에 대해서는 지정할 수 없으며,
clustered table에 대해서는 cluster level에서만 지정이 가능하다. partition
table에 대해서는 각 partition별로 pool을 지정하는 것이 가능하다.
일단 segments가 적당한 pool에 할당이 되고 난 후에는, logical hit ratio나
free buffer waits와 같은 다양한 통계 정보가 확인 가능하다.
이러한 통계 정보를 담고 있는 view는 v$buffer_pool_statistics이며,
이 view는 $ORACLE_HOME/rdbms/admin/catperf.sql을 수행하면 생성된다.

Multiple block size

Hi
When I use multiple block size tablespaces.(32K)
I have to set DB_32K_CACHE_SIZE parameter.
Assume the size of the buffer cache is 500m.
If I set DB_32K_CACHE_SIZE to 200M.
Will there be only 300m available in buffer cache? how is the allocation works?

The vast majority of databases do not need to deploy multiple blocksizes.
As noted here it is not for all databases only specific: http://www.dba-oracle.com/t_multiple_blocksizes_summary.htm
I have some doubts in this issue...When in doubt consult the official documentation and metalink.
Here is IBM's Oracle documentation on multiple blocksizes: http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP100883
While most customers only use the default database block size, it is possible to use up to 5 different database block sizes for different objects within the same database.
Having multiple database block sizes adds administrative complexity and (if poorly designed and implemented) can have adverse performance consequences. Therefore, using multiple block sizes should only be done after careful planning and performance evaluation.

Table in Keep Buffer Pool

Hi DBAs,
I need to identify the database tables and indexes which I can put in KEEP Pool. I need your hellp
How can I identify the object which are good candidate for KEEP Pool ? ( I want to put all the tables/indexes which are more than 50% in db buffer)
How can I cache these table and indexes in KEEP Pool ?
Thanks
-Samar-

Hi,
IMO tables in the KEEP pool should be relatively small, and they should fit in the pool in their entirety.
Above all those tables should be lookup tables as opposed to fact tables.
To get them in the pool
issue
alter table <table_name> storage (buffer pool keep)
Sybrand Bakker
Senior Oracle DBA

Drives, block size and raptor300 choice

Hi,
Got MacPro2,1 (07 flavour) and was planning on upgrading some internal drives. My boot is currently using two striped WD 500G's with a block size of 16k. If i were to replace these with newer drives and changed the block size to 32k, would there be any issues to speak of ? Thinking of superduper backups, Adobe CS3 licensing, Time machine doing whole boot update etc.
Alternatively i may go for a pared-down boot and use one raptor 300GB, but which one ?
WD3000BLFS / WD3000HLFS / WD3000GLFS ? - HLFS looks like the one with regularly placed SATA connections, but unsure which fits the MacPro sleds. Also is there a link for further isolation solutions eg. vibration dampeners.
Do the Raid Edition's of WD drives still cut the mustard in terms of performance (1TB Western Digital WD1002FBYS RE3, SATA 3Gb/s, 7200 rpm, 32MB Cache, 4.20 ms).
Many thanks
J

16k use to be slightly better for boot drive. The trouble wtih Apple's, I don't know how to change it on the fly like I can with SoftRAIDs.
Okay, so you probably might want 4 WD Veloci's for scratch, or 3 SSDs.
Any WD Black or RE3 should be just fine, 500GB up to 1TB, and then you get into 2TB Green RE4, yes, an RE Green drive edition.
The other factor is you want even more than 16GB RAM to be used as cache for primary 'scratch'.
There is a guide to photoshop acceleration and optimizing up on
http://www.macgurus.com - lower left side panel of links to articles.

Specifying segments and block size manaually

Hi, just a quick question,
But could anyone help me understand why someone may manually add segments to a table space (or is it a data file they would be added to) ? does auto extend not take care of this?
And secondly ... why would you increase or decrease the block size of a segment?... is this because you may have small or large sized rows within a table and want a block size to acompany this?
Any help would be appriciated

Hi,
In Oracle free space can be managed automatically or manually,You specify automatic segment-space management when you create a locally managed tablespace
Free space can be managed automatically inside database segments. The in-segment free/used space is tracked using bitmaps, as opposed to free lists. Automatic segment-space management offers the following benefits:
-Ease of use
-Better space utilization, especially for the objects with highly varying size rows
-Better run-time adjustment to variations in concurrent access
-Better multi-instance behavior in terms of performance/space utilization
For manually managed tablespaces, two space management parameters, PCTFREE and PCTUSED, enable you to control the use of free space for inserts and updates to the rows in all the data blocks of a particular segment. Specify these parameters when you create or alter a table or cluster (which has its own data segment). You can also specify the storage parameter PCTFREE when creating or altering an index (which has its own index segment).
see this link
http://download.oracle.com/docs/cd/B10500_01/server.920/a96524/b_deprec.htm#634923 :)

Multiple DB DBLOCK SIZE for warehouse database?Suggest

Hi All,a faculty from Oracle University told me the idea behind having the multple DB DBlock sizes in Oracle is not the performance but just for the Transporting tablespaces ....Just confirm is that true??????
Database architects here are using larger Block sizes for tablespaces for Warehouse database....which I guess is of not any use...what you say?
Thanx in Advance
Gagan

gaganahuja wrote:
Hi All,a faculty from Oracle University told me the idea behind having the multple DB DBlock sizes in Oracle is not the performance but just for the Transporting tablespaces ....Just confirm is that true??????
Database architects here are using larger Block sizes for tablespaces for Warehouse database....which I guess is of not any use...what you say?Gagan,
one important point that is often overlooked in this discussion is that the cost based optimizer does a questionable job when dealing with objects in non-standard block size tablespaces when it comes to costing full segment scans (full table scans / index fast full scans).
The Oracle runtime engine adjusts the multi-block read size in non-standard block size tablespaces accordingly, which means that e.g. given a multi-block read count (MBRC) of 8 and a default block size of 8K it will attempt to request 64K (whenever possible, there are cases where this is not possible, reaching extent boundaries or blocks already in the buffer cache).
So in a 16K non-standard block size tablespace the MBRC will be adjusted to 4 at runtime (4*16K = 64K), and the same happens e.g. in a 2K non-standard tablespace where it will be adjusted to 32 (32*2K = 64K).
So apart from effects outlined above that might lead to a reduction of the actually requested multi-block read size there is no difference at runtime with regards to performing a full segment scan.
But unfortunately the cost based optimizer doesn't reflect this runtime behaviour properly, especially if CPU costing is enabled, which is the default in 10g and later.
I've recently run some test cases regarding this particular issue which were provided by Jonathan Lewis as part of the "Cost Based Oracle - Fundamentals" book against the 10.2.0.4 and 11.1.0.6/7 release and they show that the cost estimates are at least questionable. By the way, although I've run the tests against 10.2.0.4 and 11.1.0.6/7, they correspond to the results of previous releases, so the same applies to 10.1 and 9i as well.
For more information, see here: http://oracle-randolf.blogspot.com/2009/02/cost-based-oracle-fundamentals-test.html
Regarding thoughts about putting indexes in larger block sizes, Richard Foote has some interesting notes that try to explain why it probably won't matter in most cases: http://en.wordpress.com/tag/index-block-size/
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle (Open source Oracle GUI for Windows):
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/

Why should recyle cache should be smaller then buffer pool.

Hi,
I am going through a documnetaion, where i read that your recyle cahche should be smaller then your buffer pools and it should be use buffers more quickly then .the idea behiend having a recycle cache is that if the sql statment is tuned then put the large segmant in recycle cahche so it does not effect others segmant in cache to edge out more frequentlly then it should be?now i wanted to know that what is the reason of taknig recyle cache smaller then buffer pool and why it should use buffers more quickly then the default buffer pool?and am i putting the right picture of recycle cache ?
thanks and regards
Alok Kumar...

Hi Alok,
I asume you mean by buffer the default buffer cache, right ?
The only idea why a recycle buffer cache should be smaller than another cache can be for memory reasons: not to spend to much memory for cache. But I cannot image this should be a general guide all all kind of application ...
On the other I have the impression that your picture of the recycle cache is a little bit different to my's picture:
I only will use different caches if have very different tables and indexes (not sql stmts). Each table and index will be assigned to a cache, e.g. the default cache and the recycle cache. The goal is, as you described, to prtend small tables and indexes from ageing out of the default cache. But the access to the recycle cache is as fast as to the default cache: both are in memory. The only diference is the administration of the blocks into the cache. The recycle cache has an administration of the blocks much easier and faster as the other one.
I hope this will give you some answers (and porb. some new questions) ...
greets,
Rainer

SSD raid 0 block size?

I just installed two OCZ Vertex 2 60Gb SSD into my Mac Pro and I'm about to set them up into a Raid 0 array but I'm wondering what's the best setting for "block size" on these? The volume will be used as system/apps/lightroom-catalog primarily. Thanks!

I've seen this same question here a few times, and the answer is almost always "leave it at the default".
From what I've read, nobody could ever notice the difference between the different sizes.
I have a RAID 0 with 2 WD Black drives (1TB each) and the standard block size (think its 32000 or something along those lines, maybe just 32, i can't remember how it's measured) and i use it for PS, Aperture etc etc, and It is lightening fast.
Regards

Query about Keep Buffer Pool and Recycle Buffer Pool

What will Keep Buffer Pool and Recycle Buffer Pool contains actually in Database Buffer Cache, specially what type of objects? I know the definitions but need to know the practical aspects about them.

918868 wrote:
What will Keep Buffer Pool and Recycle Buffer Pool contains actually in Database Buffer Cache, specially what type of objects? I know the definitions but need to know the practical aspects about them.I believe you have already got the answer from the experts. Just to echo the same, in any cache, either Buffer Cache(default), Keep or Recycle, its going to be data buffers which are actually the placeholders for the data blocks that are available on the disk. The default cache is going to throw away the lesser used buffers as fast as possible. And if you don't want this to happen, you can use either of the other two, indepandant caches-Recycle and Keep. The keep cache , as the name suggests would keep the buffers in it for a more loonger duration compared to the default cache. This probably would be a better idea when you know that some buffers are meant to be reused again and again. Recycle is going tobe for those, which are very seldom used and you don't want them to choke up the caches at all. For the buffers kept in the Recycle cache, they would be thrown out almost instantly.
Read the link that's given to you. It contains a lot of stuff that would further make things clear.
Aman....

Script to find out table and index candidates to keep in the buffer pool

I am looking for a script to find out tables and indexes to keep in the buffer pool.
Could you help me on this ?
thanks...
Markus

this is more of a open question. As you know ur data well. We do not know whats ur data. cachin tables in buffer pool is okay, but it might age out after not being used...instead you can use the KEEP POOL...to cache small tables/popular tables into the keep pool...as keep pool guarantees full caching .....
here are some links on keep pool cacheing
http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/memory.htm#sthref410
http://www.dba-oracle.com/oracle_tips_cache_small_fts.htm
http://www.dba-oracle.com/t_script_automate_keep_pool_tables_indexes.htm
http://www.dba-oracle.com/oracle_news/news_caching_keep_pool_large_objects_clob_blob.htm
Edited by: user630084 on Apr 8, 2009 5:48 AM

Db_keep_cache_size shows 0 when i keep object in KEEP buffer pool !

Dear Frineds ,
I use Oracle 10g . Form the oracle 10g documentaiton, I get the following information regarding ASMM (Automatic Shared Memory Management) :
The following pools are manually sized components and are not affected by Automatic Shared Memory Management:
Log buffer
Other buffer caches (such as KEEP, RECYCLE, and other non-default block size)
Fixed SGA and other internal allocations
Now plz see the following examle :
1) SQL> select sum(bytes)/1024/1024 " SGA size used in MB" from v$sgastat where name!='free memory';
SGA size used in MB
247.09124
2) SQL> show parameter keep_
NAME TYPE VALUE
db_keep_cache_size big integer 0 (Here db_keep_cache_size is 0 )
3) Now I keep the scott's dept table to KEEP cache :
SQL> select owner,segment_type,segment_name,buffer_pool from dba_segments where buffer_pool != 'DEFAULT';
no rows selected
SQL> alter table scott.dept storage(BUFFER_POOL KEEP);
Table altered.
SQL> select owner,segment_type,segment_name,buffer_pool from dba_segments where buffer_pool != 'DEFAULT';
OWNER SEGMENT_TYPE SEGMENT_NAME
SCOTT TABLE DEPT
4)
After doing this , I have to see the following parameter :
SQL> show parameter keep
NAME TYPE VALUE
db_keep_cache_size big integer 0
SQL> select sum(bytes)/1024/1024 " SGA size used in MB" from v$sgastat where name!='free memory';
SGA size used in MB
246.76825
Here I see that my sga is used but "db_keep_cache_size" still shows the '0' .
Can u plz explain why this parameter value shows '0' now ?
Thx in advance ... ...

Hi,
I am not sure I have understood the question fully but if you are trying to monitor usage of the buffer pools you should use some of the dynamic views like in the example query below. If this is not what you are interested in let me know.
SELECT NAME, BLOCK_SIZE, SUM(BUFFERS)
FROM V$BUFFER_POOL
GROUP BY NAME, BLOCK_SIZE
HAVING SUM(BUFFERS) > 0;

Buffer pool keep and multiple db block sizes

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