DB02:Space management/Segments/Most allocated extents in any segment

Hi ,
in My SAP server: DB02 > Oracle Database Administration > Alerts > Alert monitor, there are few red alerts.
1. Space management > Segments >Most allocated extents in any segment 263 > 200 - 263 > 200: number of extents > threshold 03.03.2009 09:35:46
in RZ20 Most allocated extents in any segment having thersold value :200
Can anybody knows what it is about? How to fix this? And what are the risks if I ignore this?
with Regards
Harinatha Reddy M

Hi,
What is your Oracle database version.? If it is 9i or 10g then you can ignore this warning as from Oracle uses Localy managed Tablespaces.
Please check below mentioned SAP notes, it may help you.
Note 599694 - LMTS autoallocate: Extent allocation
Note 706625 - Oracle9i: Locally managed SYSTEM tablespace
Note 214995 - Oracle locally-managed tablespaces in the SAP environment
Thanks,
Sushil

Similar Messages

Most allocated extents in any segment

hi gurus
My db is oracle with HP-UX In rz20 -- database-oraclesegmentsin that most allocated extents in any segment- is showing red.how to rectify this problem. and y its shoing red wht is the problem and how can i solved this.
thanks/regards

Hi,
If you are using Locally managed tablespace ( by default as of Oracle 9i), then you dont have worry about this warnings.
High number of extents is not a problem in LMTS.
Please check the below link & sap notes
http://help.sap.com/saphelp_nw70/helpdata/EN/25/5215e970077e4fb366e5ce25629aac/frameset.htm
Note 599694 - LMTS autoallocate: Extent allocation
Note 706625 - Oracle9i: Locally managed SYSTEM tablespace
Note 214995 - Oracle locally-managed tablespaces in the SAP environment
Hope this helps.
Thanks,
Sushil

Most allocated extents in any segment 6836

Hi all,
I have read a lot about reorg tables but the problem I have is that the tablespace causing us problems is SYSTEM.
Extents Owner Segment name Segm.type Tablespace
9,718 SYS C_OBJ#_INTCOL# CLUSTER SYSTEM
We are running Oracle 10.2.0.4.0 on BI7 EHP1
SYSTEM tablespace has Extent Management set to DICTIONARY all the others are LOCAL.
How do I go about solving this? I'm new to SAP BASIS work and I am no DBA.
Thanks
Craig

Hi Craig,
I do not have any guide on this.
For additional reference you may look into SAP help.
Recreating a Database with BR*Tools (SAP Library - SAP Database Guide: Oracle (BC-DB-ORA-DBA))
Recreate Database (SAP Library - SAP Database Guide: Oracle (BC-DB-ORA-DBA))
As per SAP note 748434
Logically, this results in the SYSTEM tablespace being "reorganized". The UNDO and TEMP tablespaces are also recreated in this case. However, no SAP data (series) is moved and only the SAP tablespaces (metadata) are exported and imported
Note 2:
Although no SAP data is exported or imported during the process, it is very time consuming and can take several hours.
Note 3:
Perform a complete database backup (preferably offline) before you begin the reconstruction. If the BRSPACE run terminates, the process cannot continue, and you must reset the entire database (with the "reset" function of BRRECOVER, for example).
Keep above points in mind before you execute dbcreate. Test this process on test environment first to estimate the time take and issues (if any).
Hope this helps.
Regards,
Deepak Kori

Segments with many allocated extents

Dear all,
This is regarding the number of allocated extents in any segments.
Our environment is SAP ECC 6.0 in ORACLE (11.2.0.2.0) in AIX.
We are having 2218 allocated extents for table BSIS in the tablespace PSAP<SID>.
The table is 114GB in size and have the default value 2147483645 as max.extents.
Like the same we have around 30 to 40 tables having more than 200 allocated extents.
The CCMS monitoring templates have all these tables in RED for the node 'Most allocated extents in any segment'.
I have tried online reorg for some of these tables and the number of extents gets increased at times.
How can we decrease the number of extents for such tables.
Regards,
Kiran

Kiran,
As others have stated, you do NOT want to waste your time reorganizing a table or index due to the number of extents (most of the type anyway).
First, let's determine what type of tablespaces you have:
sqlplus "/as sysdba"
set lines 132 pages 100
select TABLESPACE_NAME, NEXT_EXTENT, EXTENT_MANAGEMENT, ALLOCATION_TYPE, SEGMENT_SPACE_MANAGEMENT from dba_tablespaces order by 1;
For example here are my tablespaces I have created:
TABLESPACE_NAME NEXT_EXTENT   EXTENT_MAN ALLOCATIO     SEGMEN
PSAPGLPCAD    524,288,000          LOCAL           UNIFORM          AUTO
PSAPGLPCAI2                         104,857,600 LOCAL      UNIFORM   AUTO
PSAPMEDD                            524,288,000 LOCAL      UNIFORM   AUTO
PSAPMEDI2                           104,857,600 LOCAL      UNIFORM   AUTO
PSAPSR3                                         LOCAL      SYSTEM    AUTO
PSAPSR3701                                      LOCAL      SYSTEM    AUTO
PSAPSR3USR                                      LOCAL      SYSTEM    AUTO
PSAPTEMP                            104,857,600 LOCAL      UNIFORM   MANUAL
PSAPUNDO2                                       LOCAL      SYSTEM    MANUAL
PSAPVBFSD2                          524,288,000 LOCAL      UNIFORM   AUTO
PSAPVBFSI2                          524,288,000 LOCAL      UNIFORM   AUTO
PSAPVBOXD                           524,288,000 LOCAL      UNIFORM   AUTO
PSAPVBOXI2                          524,288,000 LOCAL      UNIFORM   AUTO
SYSAUX                                          LOCAL      SYSTEM    AUTO
SYSTEM                                          LOCAL      SYSTEM    MANUAL
If your main tablespace PSAPSR3 is LOCALLY managed as shown by the "EXTENT_MANAGEMENT" and the ALLOCATION_TYPE is SYSTEM, then Oracle will determine the NEXT extent sizes and you do not have to worry about it.
Now the reason you don't really have to worry about extents is that when SAP sends a SQL statement, Oracle determines the execution plan and then Oracle will read date by Oracle blocks NOT by extents. So in R/3 the CBO almost always picks an index as the leader and that means we read the root -> branch -> leaf -> table blocks. We do NOT read by this extent and then that extent. Even FULL TABLESCANS are reading block ranges based on the db_file_multiblock_read_count value.
Usually the only time we have EXTENT issues is if the tablespace is of type DICTIONARY instead of LOCAL. A DICTIONARY managed tablespace has a different extent management process (UET$ and FET$). Having too many extents in a DICTIONARY managed tablespace "can" cause performance problems but usually only when you are DBA tasks like reorgs because of how Oracle manages the extents and the locking process for the UET$ and FET$. This does not mean the DICTIONARY managed tablespace are bad, just that we have to keep an eye on the extents.
If your tablespaces are LOCAL then your system is configured properly. If you like, you reorg very large objects into their own tablespaces as I have done, but I do this because of archiving and frequent reorgs to seperate tablespaces so I can just drop the old tablespace. Plus I planned this during a unicode conversion so I don't have to actively manage this over time.
And as a little big more information, when we use LOCALLY MANAGED AUTOALLOCATE type tablespaces, Oracle uses a formula for the extent sizes. That way, this frees up the DBA (usually) from having to maintain extents and such. What Oracle does is create the 1st 15 extents as 64K, then the batch of extents will be at 1 Mb, then 8 Mb, then 64 Mb. That's why the AUTOALLOCATE makes it "easier" for administration. When we create LOCALLY MANGED UNIFORM tablespace, we decide how large each extent will be an every object that is put in that tablespace will have the same extent sizes (good for very large objects).
You can test this with:
create table sapsr3.kiran (t1 number) tablespace psapsr3;
alter table sapsr3.kiran allocate extent;
........ keep adding extents to see how they change over time.
col segment_name format a20
set lines 132 pages 100
select segment_name, extent_id, bytes from dba_extents where segment_name = 'KIRAN' order by extent_id;
So that's the rational behind extents. I hope it helps.
Good luck.
Mike Kennedy

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.

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 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 ?

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

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

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?

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?

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;

Datafile - space management

Hi,
Which is teh best practice in creating a tablespace? We have our production db on solaris. We are in teh process of migrating teh db into a linux box.
Our tablespaces comprises of one datafile each, and these datafiles are of size mostly over 3-4 gb
Is it advisable to create tablespace with multiple datafiles( eg three datafiles of one 1gb each) so that this I/O overhead is distributed equally among teh files.
Suppose tehre are more than one datafile for a tablespace..
How does data get stored in these files? I mean does these files get filled concurrently or does the second datafile start filling up only after the first datafile runs out of space?
Pls advise..
I want to know whether i have to split the large datafiles i have for my tablespaces when i create these tablespaces in teh linux box.
Pls advise

Hi,
>>I want to know how datafiles are wriitten..like if teh 2'nd datafile starts filling only if teh 1'st datifile is filled up
No. There is no order or rule for DBWn background process to writes on data files when a tablespace there are many data files, and 2'nd datafile can be used even if 1'st is not complete filled.
Look at the example below:
SYSTEM@teste> create tablespace test
2      datafile
3      '/u01/oradata/BDRPS/test01.dbf' size 5M,
4      '/u01/oradata/BDRPS/test02.dbf' size 5M,
5      '/u01/oradata/BDRPS/test03.dbf' size 5M,
6      '/u01/oradata/BDRPS/test04.dbf' size 5M,
7      '/u01/oradata/BDRPS/test05.dbf' size 5M,
8      '/u01/oradata/BDRPS/test06.dbf' size 5M
9      extent management local segment space management auto;
Tablespace created.
SYSTEM@teste> select   FILE_NAME AS DATAFILE,
2           d.TABLESPACE_NAME AS TABLESPACE,
3           d.BYTES/1048576 as SIZE_MB,
4           ROUND(sum(nvl(e.BYTES,0))/1048576) as USED_MB,
5           (round(sum(nvl(e.BYTES,0)) / (d.BYTES), 4) * 100) AS PERC_USED,
6           ROUND((d.BYTES - nvl(sum(e.BYTES),0))/1048576) AS FREE_SPACE_MB
7 from     DBA_EXTENTS e,    DBA_DATA_FILES d
8 where    d.FILE_ID = e.FILE_ID (+) AND d.tablespace_name = 'TEST'
9 group    by FILE_NAME, d.TABLESPACE_NAME, d.FILE_ID, d.BYTES, STATUS
10 order    by d.TABLESPACE_NAME, d.FILE_ID;
DATAFILE                                 TABLESPACE                        SIZE_MB    USED_MB PERC_USED FREE_SPACE_MB
/u01/oradata/BDRPS/test01.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test02.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test03.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test04.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test05.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test06.dbf            TEST                                    5          0          0             5
6 rows selected.
SYSTEM@teste> create user scott identified by tiger default tablespace test quota unlimited on test;
User created.
SYSTEM@teste> grant connect to scott;
Grant succeeded.
SYSTEM@teste> connect scott/tiger@teste;
Conectado.
SCOTT@teste> create table emp (cod number);
Table created.
SCOTT@teste> begin
2    for i in 1..100000
3    loop
4     insert into emp values (i);
5    end loop;
6 end;
7 /
PL/SQL procedure successfully completed.
SCOTT@teste> commit;
Commit complete.
SCOTT@teste> connect system/manager@teste
SYSTEM@teste> select   FILE_NAME AS DATAFILE,
2           d.TABLESPACE_NAME AS TABLESPACE,
3           d.BYTES/1048576 as SIZE_MB,
4           ROUND(sum(nvl(e.BYTES,0))/1048576) as USED_MB,
5           (round(sum(nvl(e.BYTES,0)) / (d.BYTES), 4) * 100) AS PERC_USED,
6           ROUND((d.BYTES - nvl(sum(e.BYTES),0))/1048576) AS FREE_SPACE_MB
7 from     DBA_EXTENTS e,    DBA_DATA_FILES d
8 where    d.FILE_ID = e.FILE_ID (+) AND d.tablespace_name = 'TEST'
9 group    by FILE_NAME, d.TABLESPACE_NAME, d.FILE_ID, d.BYTES, STATUS
10 order    by d.TABLESPACE_NAME, d.FILE_ID;
DATAFILE                                 TABLESPACE                        SIZE_MB    USED_MB PERC_USED FREE_SPACE_MB
/u01/oradata/BDRPS/test01.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test02.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test03.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test04.dbf            TEST                                    5          0          0             5
/u01/oradata/BDRPS/test05.dbf TEST 5 1 20 4
/u01/oradata/BDRPS/test06.dbf TEST 5 1 20 4
6 rows selected.
SYSTEM@teste> connect scott/tiger@teste;
Connected.
SCOTT@teste> insert into emp select * from emp;
100000 rows created.
SCOTT@teste> /
200000 rows created.
SCOTT@teste> commit;
Commit complete.
SCOTT@teste> insert into emp select * from emp;
400000 rows created.
SCOTT@teste> rollback;
Rollback complete.
SCOTT@teste> connect system/manager@teste
Connected.
SYSTEM@teste> select   FILE_NAME AS DATAFILE,
2           d.TABLESPACE_NAME AS TABLESPACE,
3           d.BYTES/1048576 as SIZE_MB,
4           ROUND(sum(nvl(e.BYTES,0))/1048576) as USED_MB,
5           (round(sum(nvl(e.BYTES,0)) / (d.BYTES), 4) * 100) AS PERC_USED,
6           ROUND((d.BYTES - nvl(sum(e.BYTES),0))/1048576) AS FREE_SPACE_MB
7 from     DBA_EXTENTS e,    DBA_DATA_FILES d
8 where    d.FILE_ID = e.FILE_ID (+) AND d.tablespace_name = 'TEST'
9 group    by FILE_NAME, d.TABLESPACE_NAME, d.FILE_ID, d.BYTES, STATUS
10 order    by d.TABLESPACE_NAME, d.FILE_ID;
DATAFILE                                 TABLESPACE                        SIZE_MB    USED_MB PERC_USED FREE_SPACE_MB
/u01/oradata/BDRPS/test01.dbf TEST 5 2 40 3
/u01/oradata/BDRPS/test02.dbf TEST 5 2 40 3
/u01/oradata/BDRPS/test03.dbf TEST 5 1 20 4
/u01/oradata/BDRPS/test04.dbf TEST 5 1 20 4
/u01/oradata/BDRPS/test05.dbf TEST 5 2 40 3
/u01/oradata/BDRPS/test06.dbf TEST 5 2 40 3
6 rows selected.You can see that the data files are been writing without a specific order.
Cheers

DB02:Space management/Segments/Most allocated extents in any segment

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