Manual segment space management and LMT

hi,
I am reading a book that says:
Using manual space management requires the DBA or the creator of the segment to specify values for the PCTFREE, PCTUSED, FREELISTS, and FREELIST GROUPS parameters when creating the object and maintaining them as the volume of segment data increases.
EXAM TIP PCTFREE, PCTUSED, FREELISTS, and FREELIST GROUPS can be set only for dictionary-managed tablespaces.
This confuses me. Surely a LMT can have objects that have MSM and not ASSM, if so, why can those not objects have PCTFREE, PCTUSED, FREELISTS, and FREELIST GROUPS set?
thanks

sybrand_b wrote:
Confusion can best be resolved by referring to the official documentation (as opposed to cluttering up this forum full of doc questions with further doc questions).
Is there any particular reason (your boss beats you up when he sees you reading documentation) why you can't be bothered to visit http://tahiti.oracle.com, or do you -mistakingly- think this is an online chatroom, instead of an offline forum?
Sybrand Bakker
Senior Oracle DBAwhat kind of an answer is that? I mean, what is the points of books if docs were everything one ever needed? I have read something in a book that confuses me, and I disagree with, but maybe my understanding is wrong, so that is why I am come here to ask others for their opinion. What is wrong with that?

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Manual segment space managed tablespaces , How tune?

I use Manual segment space managed tablespaces.
How I can tuning for high performance?
What's advantage and disavantage of Manual segment space managed tablespaces and Auto segment space managed tablespaces?
if I used more data.
I'll use Auto or manual?
Please introduce me.

ASSM deal with freelist, freelist group(RAC) storage parameters. If you use ASSM you dont need to worry about adjusting freelist and group, oracle will automatically deal with it. If you are using manual storage segment management there would no problem unless you you see heavy buffer busy waits on your tables. You may also play with freelist value for tables which have concurrent inserts and access to avoid buffer busy waits.
From oracle 9i Rel 2 onwards, you have segment level statistics to find out which segments causing more buffer busy waits and tune them accordingly. There are other meaning for buffer busy waits, check v$event_name for buffe busy waits and find out the reason code for the cause of buffer busy waits event.
Jaffar

Manual segment space management / want to shrink through segment advisor

I am trying to free space from table space , but i can't check the manual segment space manageme tablespaces, only auto segment space management allow me to do so. How i can do that?
any suggestions.

sybrand_b wrote:
Confusion can best be resolved by referring to the official documentation (as opposed to cluttering up this forum full of doc questions with further doc questions).
Is there any particular reason (your boss beats you up when he sees you reading documentation) why you can't be bothered to visit http://tahiti.oracle.com, or do you -mistakingly- think this is an online chatroom, instead of an offline forum?
Sybrand Bakker
Senior Oracle DBAwhat kind of an answer is that? I mean, what is the points of books if docs were everything one ever needed? I have read something in a book that confuses me, and I disagree with, but maybe my understanding is wrong, so that is why I am come here to ask others for their opinion. What is wrong with that?

How to change segment space management (to manual)

How do I change the segment space management for a tablespace, from auto to manual
I can find documentation, to create tablespaces, and set them to auto, but nothing yet to change them from auto to manual.

I just found out, that I am confusing 2 subjects here: segment space management, and auto extensibility. My apologies ....... still new with Oracle :-o
Ok, to change autoextend to manual, do I do this on data_file level ? Do I only need to change this on the last datafile of a tablespace ?

Difference between extent management and segment space management

Hello,
Could you tell me the difference between extent management and segment space management interms of datablocks?

After 10g, default tablespace is locally managed and with this creation, your segment's spaces are managed "automatically".
Automatic segment space management is onlyt avaliable to locally managed tablespaces.
The logic of the automatic segment space management is;
For instance, we have a rectangle cube which is totally empty (1 extent - 8 segments - 64 block in default). If we enter a new data to our table, data is stored inside this cube with it's information. (default 8k). If our data must be splitted, check row chaining for further information.
At this point, oracle decides which block is filled with the entered data. It automatically fills the emty blocks. You can use this only if your tablespace is locally managed and your segment space managemet is auto.
On the other hand,
If we create dictionary managed tablespace,
Data is stored in "dictionary" (tables in SYS schema). This is a bit slower than locally managed tablespaces. So filling the extents, segments and blocks will be slow too. You need to specify the PCTUSED, FREELISTS, FREELISTS GROUPS for the storage of the data. If segment space managent is auto, you don't need to define those values.
In summary, locally managed tablespaces with automatic segment space management is Oracle's maybe the most important feature. I am not using dictionary managed tablespaces and i advice don't use it either. In the end, this is an upgrade of using segment spaces much more faster, easier and reliable, trustable.
PS: You will need to check "High Water Mark" for automatic segment space management.

Change SEGMENT SPACE MANAGEMENT from manual toAUTO

Hi, how can i to alter tablespace to SEGMENT SPACE MANAGEMENT AUTO ?
only with re-create the tablespace ?
regards
MDF

Hi,
Oracle says :
Your specification at tablespace creation time of your method for managing available space in segments, applies to all segments subsequently created in the tablespace. Also, your choice of method cannot be subsequently altered. Only permanent, locally managed tablespaces can specify automatic segment-space management.
Paolo

Segment space management

hai experts
can anyone tell me the reason why system tablespace's segment space management is manual. any link for the description

thanks Jonathan Ferreira
want to know why manual management is made as
default for system tablespace
hen auto space management will reduce the burden of a
DBA and make space management easyIf I had to make a guess, I would suggest that since the system tablespace contains rollback (undo) segments, ASSM cannot be used. With ASSM, the extent size starts small (64KB) and grows to 1MB, 8MB, etc. as additional extents are added to segments.
Since regular users should not be using the SYSTEM tablespace for inserts/updates/undo, there should be minimal burden for the DBA in managing that tablespace.
Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc.

Conversion to segment space management auto

My production databases is 10gR2, tablespaces are created locally managed with segment space management manual.
I wanted to change the segment space management to AUTO.
What is the best way to do this keeping the downtime minimal?
Thanks
S~

A summary.
First, you cannot convert to ASSM. The only mechanism provided is to create a new tablespace with segment space management auto and then move all objects across from their existing tablespace. That is the only conversion mechanism provided or possible.
Second, you probably don't want to convert to ASSM anyway. It is designed to resolve the problem of massive contention for hot blocks on inserts -the kind of thing that will happen in a RAC. In a RAC, ASSM is extremely good news and you'd be mad NOT to use it. But if you don't have a RAC, then the chances of you needing ASSM are much less. If you find particular segments that suffer from insert contention (the symptoms are lots of buffer busy waits and ITL waits), then move those few segments that need the ASSM treatment into specially-created ASSM tablespaces. But don't go doing bulk converts of things that don't need it!
Third, if you are using OMF and ASM, then that's another situation in which ASSM makes a lot of sense: you're automating everything else anyway, so why not use the automatic 'freelists' mechanism, too?
Fourth, ASSM is about how a table knows where its next insert will take place. Extent Management Local/Uniform is all about how a tablespace allocates chunks of space to segments that need it. Completely different technologies.
Fifth, I would always use extent management auto, because do you know what are the "right" extent sizes to allocate to tables? No, I didn't think so. Oracle can work it out for you, though, with no detriment to you, your tables or your performance levels.
Sixth, back on the topic of ASSM, you might find this article useful:
http://www.dizwell.com/prod/node/541

ASSM (Automatic Segment Space Management)

Hi Folks.
I have a severe problem regarding Buffer Busy Waits.
I have deceided to implement ASSM (Automatic Segment Space Management).
Please assist....is the approch OK & how should i apply this in a existing tablespace (pls also specify the syntax & other constraints that should be taken care of)....
Waiting for reply ... & thanks a lot in advance....

ASSM is a good feature to use, but, you need to kill the culprit instaed of simply MOVING ON.
If creating a new tablespace with ASSM, moving objects from Non-ASSM to the new tablespace is a problem, then, think of the following:
First of all, findout which object type is causing BBW, is it rollback/undo header, undo/rollback block, segment headere or what?
You need to review the P3 value(reason code) of BBW wait event.
Try to review the following dynamic views, before you decide to MOVE on.
v$waitstat (segment header)
v$segment_statistics(read the oracle docs. how to use this view and which parameter need to set in order to enable this feature).
Jaffar

How to identify the SEGMENT SPACE MANAGEMENT is AUTO turned ON

how to identify the SEGMENT SPACE MANAGEMENT is AUTO turned ON for a particular tablespace.

Hello,
Try:
SELECT tablespace_name, file_name, autoextensible
FROM DBA_DATA_FILES
ORDER BY tablespace_name, file_name;Oops, wrong answer, try:
SELECT tablespace_name, segment_space_management
FROM dba_tablespaces
order by tablespace_name;

How to change manual segment management to automatic? and vice versa

how to change manual segment management to automatic? and vice versa
i can't find any option for that in EM
Thanks

Paolo Marin,
The original wants to change from Freelist management to Automatic Segment Space management - the URL you supplied is about converting from Dictionary Managed tablespaces (DMT) to Locally Managed tablespaces (LMT).
In passing - the article you reference says: First, MAKE sure to take a full backup of the tablespace and all related tablespaces (inter-tablespace referential integrity) before running this procedure:. There's no such thing as 'tablespace referential integrity', but (a) it would be a good idea to make sure that no-one else is using the database whilst you do a conversion, and (b) it's the system tablespace that holds the data dictionary so that's the one other (really important) tablespace you have to back up before starting.
There is a very old note about the limitations of doing the DMT -> LMT conversion here: http://www.jlcomp.demon.co.uk/book_8i/ch_08.html#Extent%20Management
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
https://www.jlcomp.demon.co.uk

Segment space for Manual tablespace management

Hi,
wanted to know if 10g segment advisor can advise on segments that exsists in a tablespaces that is set to manual extent management.
thanks,
Ven.

From the
Oracle® Database Administrator's Guide
10g Release 2 (10.2)
Part Number B14231-01
14 Managing Space for Schema Objects
Understanding Reclaimable Unused Space
You use the Segment Advisor to identify segments that would benefit from online segment shrink. Only segments in locally managed tablespaces with automatic segment space management (ASSM) are eligible. Other restrictions on segment type exist. For more information, see "Shrinking Database Segments Online".

Migration LONG to LOB in manual space management tablespaces

Hi everyone,
We have Netweaver 7.0 and Oracle 11g and we are considering to migrate our manual tablespaces to ASSM. The first problem we've found is we can't do that online due to the LONG data type. So we decided to migrate LONG to LOB first. Note 835552 says that for Oracle version 11g the conversion is from LONG to SECUREFILE. But we follow seeking notes and in 1426979 (Oracle 11g: SecureFiles - The new way to store LOB data) one of the prerequisites for the conversion is to use ASSM tablespaces.
At this point, we can't migrate (online) to ASSM due to LONG data and neither can migrate to SECUREFILE due to the ASSM.
My question is: is it possible to make the migration from LONG to SECUREFILE specifying in the brspace a new tablespace with ASSM?
Thanks in advanced.

Hello
It is in fact possible to reorganize segment to a specific target tablespace using brspace option -n|-newts
brspace -u / -f tbreorg -a long2lob -o sapsr3 -s <source_tablesapce> -t allsel -n <target_tablespace_in_ASSM>
It is odd that in 11g you are not in ASSM, so you upgrade to that version and never performed tablespace reorg ?
620803 - Oracle 9i: Automatic Segment Space Management
The new ASSM function is available as of Oracle Release 9i. As of Oracle 10g, ASSM is already contained in the standard system, and new tablespaces are by default created as ASSM tablespaces.
Regards

Difference between extent management and segment management

friends what is the basic difference between extent management and segment management,as we know that segment is a collection of extents then why is it necesassry to manage both??..and what is the need to do so?

saugat chatterjee wrote:
friends what is the basic difference between extent management and segment management,as we know that segment is a collection of extents then why is it necesassry to manage both??..and what is the need to do so?Oracle stores data in it's own logical structure.
Blocks --> Extent --> Segment
Oracle block(also known as page) being the granular level where the data is stored. Extent is a collection of blocks.
When you specify extent management, you mean where the allocation/de-allocation of extents(group of blocks) will be managed (either in dictionary or using bitmaps).
When you specify segment space management, you mean that how the space inside a block will be managed. Extent management doesn't control space distribution inside block.
Regards,
S.K.

Segment space mangement

Hello Folks,
For Oracle 10g its recommended Segment space management as auto by oracle
but do it have any limitations
I understand for changing from manual to auto need to recreate tablespaces,is it worth change from manual to auto
i mean do it provides considerable benefits in long run, i see some dba still prefer manual (pl suggest reason if anyone aware)
Thanks in advance
dev

In case of auto, no need to specify the PCTUSED, FREELISTS, and FREELIST GROUPS parameters

Manual segment space management and LMT

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