Bit Map Indexing

Hi All
i have a table with 5.5 million records and i have a fields (project id and owner id) with 8400 and 507 distinct values. For reporting reasons i want to create a bit map index on the project id. My question is even though it makes the query faster will it take more space? How can i calculate how much space it takes? Secondly if the ROI is not good for creating index on the project id can i creat index on the second field (owner id) and can still make the query faster?
Thanks

897837 wrote:
i have a table with 5.5 million records and i have a fields (project id and owner id) with 8400 and 507 distinct values. For reporting reasons i want to create a bit map index on the project id. My question is even though it makes the query faster will it take more space? Strange question - indexes are an overhead. Space is needed for an index structure. The structure needs to be maintained when data is added, changed or deleted.
The question is whether these overheads are justified by the increase in performance when reading the table structure for selected rows and using the index structure as part of process to get to those selected rows.
So it is not only space that is the coin of payment for indexes. There's also extra CPU to burn in order to maintain those indexes.
How can i calculate how much space it takes? Well, today I would say that space is much less of a consideration. Disk space is cheap. Overheads to maintain additional data structures are not cheap. So I would first look at the performance impact. If you need to maintain a 100 rows/sec insert rate for example, you can ill afford overheads that do not pay back with time gained when reading data.
I would also want to measure just how much the index reduces the workload for reading data. Does it decrease the read I/O load by 1% or 50% ?
You need to quantify the impact of that index to determine whether it is worthwhile. And it does not mean merely calculating the cost ito space used and then see how fast it makes a query by using a stop watch or timer (the wrong metric for measuring SQL performance).

Similar Messages

Creating a bit map index on a partitioned table

Dear friends,
I am trying to create a bitmap index on a partitioned table but am receiving the following ORA error. Can you please let me know on how to create a local bit map index as the message suggests?
ERROR at line 1:
ORA-25122: Only LOCAL bitmap indexes are permitted on partitioned tables
Trying to use the keyword local in front leads to wrong syntax.
Thanks in advance !!
Somnath

ORA-25122 Only LOCAL bitmap indexes are permitted on partitioned tables
Cause: An attempt was made to create a global bitmap index on a partitioned table.
Action: Create a local bitmap index instead
Example of a Local Index Creation
CREATE INDEX employees_local_idx ON employees (employee_id) LOCAL;
Example is about btree and I think it will work for bitmap also.

How to set the option Bit-mapped indexes to true ?

Hi,
I a not a an Oracle Administrator. Usually, I just use Oracle as developper. I have got a Oracle 10g database. I can not import data in my database because the Bit-mapped options is not set.
When I type
select banner from v$version
I get this result :
BANNER
Oracle Database 10g Release 10.2.0.1.0 - Production
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production
I run the import and I get this error :
IMP-00017: following statement failed with ORACLE error 439:
"CREATE BITMAP INDEX "ID_ACC_DO" ON "ES_AUDIT_CONNEXION_ARCH" ("DATE_OUVERTU"
"RE" ) PCTFREE 10 INITRANS 2 MAXTRANS 255 STORAGE(INITIAL 33554432 FREELIST"
"S 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT) TABLESPACE "IND_XL" LOGGING"
IMP-00003: ORACLE error 439 encountered
ORA-00439: feature not enabled: Bit-mapped indexes
I typed the command :
SELECT * FROM V$OPTION WHERE PARAMETER LIKE 'Bit-mapped%';
I get the result :
PARAMETER
VALUE
Bit-mapped indexes
FALSE
How to set this parameter to true ?
Best regards,
Xavier

I beleiev that you are on Standard Edition.Bitmap indexes can be used only when you are working with Enterprise edition.
SQL> select * from V$option where parameter like '%Bit%';
PARAMETER
VALUE
Bit-mapped indexes
TRUE
SQL> select * from V$version;
BANNER
Oracle Database 11g *Enterprise Edition* Release 11.1.0.6.0 - Production
PL/SQL Release 11.1.0.6.0 - Production
CORE 11.1.0.6.0 Production
TNS for 32-bit Windows: Version 11.1.0.6.0 - Production
NLSRTL Version 11.1.0.6.0 - Production
SQL>I guess you see the entry coming of Enterprise Edition in my banner.This is missing in your V$version, so you are using Standard Edition install.
You need to move to Enterprise edition to use Bitmap Indexes.
HTH
Aman....
Edited by: Aman.... on Dec 11, 2008 3:09 PM
added a little more.

Table name where I can see the Secondary bit map Index for Cube Loads in BI

Hello Friends I want to know the table name where I can see the Secondary bit map Index that gets created with each request that get loaded to Cube so each 1 request will be multiplied by 7 dimension and 7x1 = 7 local secondary bit map index will be created where is that table which show me that .
Under Oracle every uncompressed request corresponds to one partition in the
F facttable of the corresponding infocube. This partition also brings along
a full set of secondary local bitmap index partitions.
If you have a cube with 10 uncompressd requests and 10 dimensions (every
dimension brings with it a local bitmap index) you have 100 partitions for
the table itself and 10 x 10 index partitions which makes a total of
100 database objects. where is that table in BI WHICH STORE THIS INFORMATION
Also if I have E Table with no entries for future 2009 dentries will that be an issue with blank partition ion E Fact table if yes please suggest how to resolve this issue

Hi Soniya
Information about BI objects is stored in the RSD* tables. For example:
Infocubes: RSDCUBE / RSDCUBET
Aggregates: RSDDAGGR_V / RSDDAGGRT
You can see information on abap dictionary object as well in transactions SE11 / SE14. You will have to know the real table name of the cube, should be something like /BIC/F* for the uncompressed and /BIC/E* for the compressed table.
Best regards, Michael

How bit map index works?

I am not getting an example for bitmap index mechanism.
Supposing their is a table T1 with column c1 having records
Y
N
N
Y
Y
N
and i query the table like
select * from t1 where c1 = 'Y'
How bit map index functions?
thanks,
Vinodh

I think you should check the google's new feature to explore -> [How bitmap Index Works|http://www.google.co.in/search?hl=en&rlz=1G1GGLQ_ENIN333&q=how+bitmap+index+works&meta=&aq=0&oq=how+bitma]
Regards.
Satyaki De.

Bit Map index in DW application

Hi
I have a DW database having a table contains 9 million records. Normally for DW application bit map index is preffered if the cardinality is low.
I want to create an index on one of the column having the cardinality is about millions, so which index is preferrable?. If I go with normal indexing any performance degradation will be happen for the application? or if I used bit map indexing any improvement will be there?
Many thanks

I would go for normal index, there is a certain additional load when inserting, updating, deleting, but in that case a bitmapped index wouldn't be good idea anyway.

Bit-mapped Index

Hi,
I run this
CREATE BITMAP INDEX bx_time_period ON time_period (time_period_cd)
and i got this error:
ORA-00439: feature not enabled: Bit-mapped
I am using a Oracle 9i SE.
How can i do to fix this error ?
Do i need to install any patch
Thanks.
Leo

About differences between normal an bitmap indexes you can see [url http://download-west.oracle.com/docs/cd/B14117_01/server.101/b10743/schema.htm#sthref883]The documentation
In general, bitmap indexes are useful in application with huge data, low cardinality keys and low level of concurrent transactions (i.e. DataWarehouse), while normal indexes are tipically suitable for OLTP applications.

Bit map indexes.

Hi-
I am trying to understand the below from oracle documentation. Can someone explain the EXPLAIN PLAN for the below in simpler way. Thanks
Viewing Bitmap Indexes with EXPLAIN PLAN
Index row sources using bitmap indexes appear in the EXPLAIN PLAN output with the word BITMAP indicating the type of the index. Consider the sample query and plan in Example 12–8.
Example 12–8EXPLAIN PLAN with Bitmap Indexes
EXPLAIN PLAN FOR
SELECT * FROM t
WHERE c1 = 2
AND c2 <> 6
OR c3 BETWEEN 10 AND 20;
explain plan
SELECT STATEMENT
TABLE ACCESS T BY INDEX ROWID
BITMAP CONVERSION TO ROWID
BITMAP OR
BITMAP MINUS
BITMAP MINUS
     BITMAP INDEX C1_IND SINGLE VALUE
     BITMAP INDEX C2_IND SINGLE VALUE
BITMAP INDEX C2_IND SINGLE VALUE
BITMAP MERGE
BITMAP INDEX C3_IND RANGE SCAN
In this example, the predicate c1=2 yields a bitmap from which a subtraction can take
place. From this bitmap, the bits in the bitmap for c2 = 6 are subtracted. Also, the bits in the bitmap for c2 IS NULL are subtracted, explaining why there are two MINUS row sources in the plan. The NULL subtraction is necessary for semantic correctness unless the column has a NOT NULL constraint. The TO ROWIDS option generates the rowids
necessary for the table access.
Thanks
sk
Edited by: sk12345678 on Dec 10, 2011 7:45 PM

WHY ORACLE TALKS OF MINUSminus in the sense of the set operator *the set { {A} minus } is the set of all elements members of {A} that are not members of {B}*
<font face="courier">
           ┌───────────────┐
┌──────────┼───┐           │
│          │   │           │
│ C1 = 2   │   │  C2 = 6   │
│          │   │           │
└──────────┼───┘           │
           └───────────────┘
</font>
{C1 = 2} and {C2 != 6} ≡ {C1 = 2} minus {C2 = 6} ≡ {C1 = 2} intersect {C2 != 6} ≡ {C1 = 2} intersect complement({C2 = 6})
{1,2,3} minus {2,3,4,5,6} gives {1}True
instead should be an INTERSECTION of {1,2,3} and {2,3,4,5,6}False ( you missed the not )
an INTERSECTION of {1,2,3} and {1,7,8,9} ( you missed the not )
Regards
Etbin

Bit Map Index

how to use BitMap index and function based index.
in Oracle how its executed. how its taking data fast ??

@Prasad: lower(ename) is function based index.Like Hydrabadi Biriyani.... :)
@OP: Read the Oracle Documentation about Indexes.

ORA-00439: feature not enabled: Bit-mapped indexes

Do I need to change any parameter to enable this feature or I just can't use it in Oracle XE?
Thanks,
Allwyn

Hi Allwyn,
the feature list of XE says that Bitmapped index and bitmapped join index are not supported ( http://download-east.oracle.com/docs/cd/B25329_01/doc/relnotes.102/b25327/toc.htm#BEIDGBCD ) . I guess it won't work then.
We get the function based index, though.
Regards,
~Dietmar.

Does BI 7.0 use bit map join indexes?

I have seen several threads on SDN which show that SAP BI is using bit map indexes with Oracle database. However, it is not clear whether BI utilizes bit map join indexes or just bit map index. Bit map index is on a single table whereas bitmap join index is on a join of two or more tables.
It will make sense for SAP BI to use bit map join indexes with star transformations where a join is done among fact and dimension tables.

> Thanks. Another question, are bit map indexes used both for F and E fact tables or just for F. I am not using real-time cubes (where SAP BI uses B-Tree indexes for F table to avoid dead locks).
Why don't you simply check this in your BI system yourself?
And, yes, of course it uses bitmap indexes for both fact table types.
E-fact tables are the same as F-Facttables except that they contain the compressed/rolled up data.
regards,
Lars

Bit Map Join Index Creation

Hi,
I have a db of version 10.2.0.3 on a Unix box. This is used for DW.
I have a dbms job which is basically creates 6 bit map join indexes between two tables parallelly. One of the table (Fact table) has almost 170 million data and the other one (Dimension table) has 1.2 million data. Fact table is partioned and the indexes are local index.
For the last couple of days, this job is taking almost 70+ minutes whereas previously, it used to take around 44 to 48 minutes.
My pga_aggregate_size is 50GB and temp tablespace size is 33GB.
Per day 1 million data gets populated in the Fact table.
It used to run fine earlier. One fine morning we found this performance issue.
It will be really helpful, if we get some suggesstion about the tuning options.
Regards,
Soumyajit

Jeet wrote:
I have a db of version 10.2.0.3 on a Unix box. This is used for DW.
I have a dbms job which is basically creates 6 bit map join indexes between two tables parallelly. One of the table (Fact table) has almost 170 million data and the other one (Dimension table) has 1.2 million data. Fact table is partioned and the indexes are local index.
For the last couple of days, this job is taking almost 70+ minutes whereas previously, it used to take around 44 to 48 minutes.
My pga_aggregate_size is 50GB and temp tablespace size is 33GB.
Per day 1 million data gets populated in the Fact table.
It used to run fine earlier. One fine morning we found this performance issue.
It will be really helpful, if we get some suggesstion about the tuning options.Soumyajit,
since you probably don't have suitable data available from those runs (by "data" I mean e.g. SQL traces with row source operation statistics, wait event information and number of I/Os etc.) where it used to be faster it's going to be hard to tell where the difference comes from since there are many possibilities.
If really nothing else has changed apart from the data volume then one possible explanation could be that the join operation that is required to populate the bitmap join index switched from e.g. single pass to multi-pass due to the increased data volume.
Another explanation could be that one of the tables used to be cached in the buffer cache (small table threshold) but has now exceeded the default 2% limit for cached table scans and therefore requires more physical I/O than previously.
But there is a multitude of other possibilities starting from changes to the software/hardware (patches to Oracle, O/S, storage etc.), concurrent processes running at the same time, changes to the logging attributes of the tablespace/database, different execution plan due to statistics change, ASMM automatic cache buffer shrinkage etc. etc.
It definitely makes sense to trace the execution now to have that information available, furthermore you could try to check if the usage of the TEMP tablespace has increased in comparison to previous runs which could indicate above mentioned switch to a less efficient pass mode of the join.
Can you pinpoint already if only particular bitmap join indexes take longer than before or all six are slower than before?
Do I understand this correctly, that you run six jobs in parallel to create the indexes, or is it one job that runs the create index statements one after the other?
And do you use the PARALLEL DDL option to create each individual index? What about LOGGING/NOLOGGING?
By the way, what is reason that you rebuild the indexes every day? Is this after a load into a particular partition to rebuild the indexes of that partition after the data load? Or is it a rebuild of all partitions?
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/

Warning Msg: Character Mode report is being opened as a Bit-mapped report

Hi All,
I am opening a Oracle Standard Report in Oracle Apps "INVISMMX", while opening it shows the below warning message:
"Character Mode report is being opened as a Bit-mapped report"
What is the reason for this?
How can I open this report in ASCII mode itself?
Thanks,
Gowri

I believe Oracle Reports by default will open a report as a bit-mapped report. You can change the poperties of the report to make it a character mode report by:
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then click in the toolbar.
2. Double-click the properties icon next to the report node to display
the Property Palette.
3. Under the report node, set the width and height properties as desired:
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4. Under the Character Mode node:
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the Ruler Settings dialog box.
10. Set Units to Character Cells and Number of Snap Points Per Grid Spacing
to 1. Click OK.
11. Click View in the menu bar and make sure that Snap to Grid is checked.
12. Choose Tools Preferences to display the Preferences dialog box.
13. On the Preferences page, set Horizontal Interfield to 1 and Vertical
Interfield to 0. Click OK.
14. Choose Format Font, and select the font, style, and size that most
closely approximates the character-mode font (such as, Courier,
Regular, 12 point).

PDF displaying bit-mapped or "crunchy" on Retina MacBook Pro

I have a new Retina MacBook Pro and when I opened a PDF, it is displaying bit-mapped or "crunchy" looking. Do I need to change settings in Acrobat (CC) ?... or in my Mac System Preferences somewhere?

I can sort this out by just using a HDMI > DVI cable which works fine. I think there must just be an issue with the BenQ HDMI input supporting 1920x1200. Its annoying because the screen is also connected to a PC workstation by DVI so it would be good to have the HDMI for the Macbook so I can quickly switch the display by pressing a button instead of having to unplug cables...

IMac boots to bit-mapped rows of diaganol lines across screen & then freeze

Im not sure where to post this. Unsure if it's a start-up or a display problem - or both ...
A friend of mine was trying to install boot camp on her 17" Early 2006 but the installation failed half-way through ...
Now, when the machine is switched back on - serious square or bit-mapped looking rows of diagonal lines appear from top to bottom on the screen at 30mm gaps ... it boots up OK to the grey Apple Screen with the spinning cog below - then the lines disappear and the blue start-up screen - looks like it's about to show the 'Starting Mac OS X' window - but then stops - and the cursor changes to a weird rectangular mess - and nothing else happens ... the cursor still moves - so I know the system is not completely frozen - it just won't boot past the blue screen ...
The only way I can get it to boot to the desktop is in Safe Mode (shift key at start-up) - but it boots all the way with the diagonal lines.
Here's what I have tried so far ...
* - reset pram
* - targeted it to another intel mac and used Disk Utility to zero the hard disk to a single Mac OS Extended (journaled) partition (erasing the previous XP portion created by the botched Boot Camp assistant).
* - a clean install of Mac OS X.4.6 via a 'C' boot.
* - restarted into safe mode holding the 'shift' key to get to the desktop.
* - run software update to see if there were any new EFI or Firmware updates.
all to no avail ...
I have also scanned the Apple downloads pages and here in the discussions.
And also the Boot Camp discussions - I can find only one other post with a similar issue - but there is no 'fix' or solution posted ...
My hunch is the firmware has been affected by the boot camp installer - or something to do with the EFI parameters on the video board.
I have tried everything Apple suggests - including an attempt to reinstall the firmware via a hard press of the power button and inserting a special install firmware install CD from Apple downloads - but I can't get the firmware bar to load at start up ...
If I try reinstalling the latest firmware update - I get a message saying "Your Firmware is up to date' - or 'This update is not needed on this machine' ...
Q: Is there a stand-alone installer that will reinstall the firmware - without doing a version check - and just do a fresh firmware install ... ?
Does anyone know a way around the version check.
I am convinced this issue is a software/firmware related problem - I sense the EFI settings have screwed up the video settings on the board - and I all i want to do is refresh them.
It's still under it's initial 1 year warranty - but I'm not sure a botched Boot Camp install is covered ...
Sorry for the long post - but I'm hoping a nice apple guru can help me out with this 'very hairy' problem ..
... macfinger - auckland city
17" intel imac early 2006 1.8GHZ 512RM

OK - here's the result of the rows of diagonal lines across the screen on the 17" Intel Core Duo iMac, which I posted last week ...
The logic board was definitely faulty - it could not be repaired by firmware or otherwise ... the service centre was very vague about which area or part of the board failed - but I suspect it was the embedded video board or VRAM ...
(actually - I still reckon it was a botched firmware - but seeing as Apple's 'Open Firmware' is nor strictly 'Closed Firmware' .... there was no way of actually testing that theory for sure ...
From what my friend has told me - she said this fault was the result of a botched Boot Camp XP installation when loading the Windows drivers from the Mac generated Drivers Install CD which froze - and then trying to boot back into Mac OS X by doing a hard restart, after it failed ...
A message to any future readers of this post:
If your machine shows signs of of the above symptoms - you'll have to return it to an Authorised Apple Service Centre to have the logic board replaced (hopefully under warranty) ...
BE SURE AND BACK UP ALL OF YOUR PERSONAL USER DATA FIRST - AS THERE WILL BE NO GUARANTEE YOUR USER FOLDER WILL BE RETAINED WHEN YOU GET YOUR MACHINE BACK ...
You can still access your HD by doing a safe boot: hold the 'Apple' & 'S' keys immediately after you hear the start-up 'chimes' ....
Once you're back to your desktop - use your machines internal CD-RW/DVD to copy your files to disk ... it's a bit tricky with all the lines across the screen - but persevere - 'cause that's what we did - and we know it can be done.
Good luck ...

Bit Map Indexing

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