Similar Questions

• Index BITMAP and NOT NULL

  Hi all
  Is it possible to use the Index BITMAP for a NOT NULL condition?
  
  
  >
  
  CREATE a BITMAP of INDEX x_ix FOR tab (x);
  
  SELECT *.
  TAB
  WHERE x IS NOT NULL
  
  >
  
  Thank you!

  user3646231 wrote:
  You say that :) to hope

  Here it is:

  Your test is a good effort - but it needs a little more.

  Your question is "is it possible...". «, not "If Oracle always...» »

  Your demonstration showed an example where the choice of plan Oracle has surprised you (and me). Now, you need run the query with index indicator (because if the indexed access path is legal, must be taken an indexed correctly suggested path).

  I just ran a similar test (1 line of 100,000), with the following results:

  SQL> select * from table(dbms_xplan.display_cursor);
  
  PLAN_TABLE_OUTPUT
  ------------------------------------------------------------------------------
  SQL_ID  52q6gxkscvg9v, child number 0
  -------------------------------------
   select /*+ index(t1(n1)) */ * from t1 where n1 is not null
  
  Plan hash value: 2828957992
  
  ----------------------------------------------------------------------
  | Id  | Operation                    | Name  | Rows  | Bytes | Cost  |
  ----------------------------------------------------------------------
  |   0 | SELECT STATEMENT             |       |       |       |  1859 |
  |   1 |  TABLE ACCESS BY INDEX ROWID | T1    |     1 |   118 |  1859 |
  |   2 |   BITMAP CONVERSION TO ROWIDS|       |       |       |       |
  |*  3 |    BITMAP INDEX FULL SCAN    | T1_N1 |       |       |       |
  ----------------------------------------------------------------------
  
  Predicate Information (identified by operation id):
  ---------------------------------------------------
  
     3 - filter("N1" IS NOT NULL)
  

  You will notice that the cost of the query is unreasonable - and without the suspicion my test showed Oracle taking the full analysis at a much lower cost.
  If your test has actually demonstrated a bug in the costing, explaining why Oracle does not automatically take a path that seems reasonable.

  The above output comes from 11.2.0.3, but I had the same thing with 11.1.0.7

  Concerning
  Jonathan Lewis
  http://jonathanlewis.WordPress.com
  Author: core Oracle

• B - Tree and explanation Index Bitmap

  Hi gurus

  I am trying to absorb the notion of bitmap index and b-tree, but unable to grasp the concept, so far, I have learned the following:

  Index B-Tree

  Use in the OLTP environment

  It is customary for these types of columns where you have more unique value or we can say that high cardinality

  It occupies less storage

  Using the corresponding model and ranges

  By default, Oracle uses tree indexing

  Bitmap index

  Use in home environment/OLAP data items

  It is customary for these types of columns where repeated values exist or we can say that low cardinality, example are male and female

  It seems that these points of difference between the two indexes. I really appreciate if someone give me more explanation on these subjects.

  Thanks in advance

  Concerning

  Muzz

  I am trying to absorb the concept index bitmap and tree but unable to grasp the concept,

  Then the FIRST place to look is the Oracle documentation; specifically the chapter "Index and Index-Organized Tables" chapter of the Concepts doc.

  http://docs.Oracle.com/CD/E25054_01/server.1111/e25789/indexiot.htm

  3 indices and Index of Tables

  This chapter deals with indices, which are schema objects that can speed up access to the lines of the table and organized index of tables, which are tables stored in an index structure.

  This chapter contains the following sections:

  • Overview of index
  • Overview of the Tables organized by Index

  This chapter has a lot of basic information on ALL the various types of indexes.

  so far, I've learned the following:

  Where, exactly, 'have you' who? Most of it is wrong, incomplete or distorted.

  Index B-Tree

  Use in the OLTP environment

  Index B-Tree, by default, are used in all environments.

  It is customary for these types of columns where you have more unique value or we can say that high cardinality

  They can be used for a cardinality. True - a unique column index is most commonly used for high-cardinality columns. But Oracle may also use an index column, simple or composite, when the data being sought is ENTIRELY contained in one or more indexes, low cardinality.

  It occupies less storage

  Maybe, maybe not. It is based on the column being indexed, the size of the key values and the cardinality of the key values. For your example "Male and female" there will be only THREE index entries: male, female and null. And each entry is simply a list of ranges of ROWID. This index can be orders of magnitude smaller than the equivalent B-Tree index.

  Using the corresponding model and ranges

  For the most part correct - although the range queries can be used with the bitmap index which is not a common use.

  By default, Oracle uses tree indexing

  Fix.

  Bitmap index

  Use in home environment/OLAP data items

  Especially correct - DML on tables with the bitmap index can cause severe performance and throughput problems. The distinction is therefore between environments with medium/high DML on a table compared to the weak or nonexistent DML on a table.

  So rather than a distinction between environments (OLAP and warehouse) the distinction is no longer between the TABLES (high/medium DML versus LOW/NO DML). There is nothing wrong at all with the help of the index of the bitmap in an OLAP environment - but these indices should be limited to the tables with low, or no, DML.

  It is customary for these types of columns where repeated values exist or we can say that low cardinality, example are male and female

  Yes and no.

  Yes - a bitmap index is not really appropriate, if there is NO repeat value.

  No - part II (low cardinality). The attribute MAJOR missing from what you have posted is that bitmap indexes are ALMOST always used in conjunction with others (usually a bitmap) index.

  If one, or more, high cardinality bitmap index can be used VERY effectively together to identify a set of rows to a query.

  See my multiple responses in this thread

  https://community.oracle.com/message/10219613?

  One of my answers presents, in detail, just how many attributes can be combined using several bitmap on both high columns index and low cardinality.

  In a later response, I provide the actual sample code and display the execution plan indicating how Oracle just that.

  SQL> set serveroutput on
SQL> set autotrace on explain
SQL> select rowid from star_fact where
  2   (state = 'CA') or (state = 'CO')
  3  and (age = 'young') and (marital_status = 'divorced')
  4  and (((summer_sport = 'baseball') and (softdrink = 'pepsi'))
  5  or ((summer_sport = 'golf') and (beer = 'coors')));


  Read the full thread.

• Index Bitmap and MV in Standard edition

  Salvation of DBA
  
  I have an enterprise edition 10.2.0.3 database which can be transformed into 11.2.0.3 EE. There many Materialized view with activated query rewrite. If I downgrade to the standard edition, what will be the impact? I know the rewrite of the query is a feature of EA and not SE and SEO. It is also the index Bitmap in the database which I think must be re-created as the normal b-tree index.
  
  I know that bitmap is not a feautre of the SE. One advantage that I see that updates will be faster if there is a normal index as DML are slow, if there is a Bitmap index.
  
  What will be the impact on the performance of the database if there is standard edition which does not rewrite of the query and the characteristics of Bitmap?
  
  Thank you
  
  DBA is the hero behind the screen, while developers are heroes on the screen.

  user13368428 wrote:
  I went through this table before posting my first post. I don't know there are a lot of tables in my EE database that contains bitmap indexes. In the past, I turned on the control over some of them, and they have been used. Also, I have seen queries that are rewritten to use the MV table instead of the base of fact tables.

  Yes. Really, I need to test in decommissioning and annexing the request to it. But I wanted to know if anyone has experienced this. What were their experiences do not use Bitmap indexes, function index and Query rewrite.

  Your response was very useful.

  Thank you.

  The Oracle Server Standard edition supports function based indexes (I think since version 8.1.5). Bitmap indexes are not supported and treat B * index of tree as the index of the bitmap to bitmap join operations are also not supported. You can partially determine the impact of not having the second option by editing a hidden at the session level setting (obvious caveat on masked editing settings apply here):

  ALTER SESSION SET "_B_TREE_BITMAP_PLANS" = FALSE;
  

  I'm fairly certain that the Standard Edition supports materialized views - automatic query simply not rewrite for possibly enjoy this feature based on cost.

  There may be a few other surprises, here is part 1 of 4 that explores the potentially unexpected differences between Standard Edition and Enterprise Edition (the differences are version and OPTIMIZER_FEATURES_ENABLED load):
  http://hoopercharles.WordPress.com/2010/11/21/different-performance-from-Standard-Edition-and-Enterprise-Edition-1/

  Good luck to you with the project.

  Charles Hooper
  http://hoopercharles.WordPress.com/
  IT Manager/Oracle DBA
  K & M-making Machine, Inc.

• Index bitmap for FKs on fact tables

  Hi all
  
  We have a database of DWH (Star Dimesions and the tables schema) running with OBIEE 11 g (11.1.1.1.6) on the oracle 11 g (11.2.0.1) database. I read in one of the best practical paper, creating index Bitmap on the Fks of all fact tables will help performance.
  
  I created indexes for the less than 2500 separate keys, but we have 2 dimesions tables where there are great number of records (size 14 g and 10 g). Can I go ahead and create indexes of bitmap for 2 tables establishments (mainly account_key and customer_keys are the columns)?
  
  Worried about creating index bitmap for large tables where they could affect the ETL process.
  
  Ref: http://www.oracle.com/technetwork/database/bi-datawarehousing/twp-dw-best-practies-11g11-2008-09-132076.pdf (page 20)
  
  Help, please.
  
  Thank you and best regards,
  Anand.

  >
  I created indexes for the less than 2500 separate keys, but we have 2 dimesions tables where there are great number of records (size 14 g and 10 g). Can I go ahead and create indexes of bitmap for 2 tables as well
  . . .
  Worried about creating index bitmap for large tables where they could affect the ETL process.
  >
  You put the cart before the horse!

  Don't create index unless you have a reason documented for them.

  Why did you choose the index bitmap for cardinality less than 2500? Perhaps based on a long-standing myth, but discredited on the cardinality?

  See also Richard Foote two articles where he explodes the myths about bitmap indexes and considerations of cardinality
  http://richardfoote.WordPress.com/2010/02/18/myth-bitmap-indexes-with-high-distinct-columns-blow-out/
  http://richardfoote.WordPress.com/2010/03/03/1196/

  Re your concern about the tables with the 'large' number of records and affecting ETL.

  You are right to be concerned about these issues, but you need to document your particular situation taking into account the architecture.

  The fact tables and dimension tables can have a large number of records. If using the bitmap index is indicated, then the most records are most effective, they will be.

  ETL is affected because the DML (INSERT, UPDATE, DELETE) operations on the tables with bitmap indexes can have serious performance because of the involved serialization issues. Updated single bitmap of a column value (e.g., am ' to 'F' gender) requires that the two index bitmap blocks must be blocked until the update is complete. An index of stored bitmap ranges ROWID (rowid min - max rowid) that can span many, many files. The "range" of ROWID is locked in order to change a value.

  To change: 'follow her' rowid beach so that a row is locked and ID should be removed from the range by turning off the bit. Change to the 'F', the rowid id range 'F' must be found, locked and the bit set that corresponds to this rowid. No another row with ROWID in the range cannot be changed, because it is a transaction in the series. If the range includes 1000 lines and they all need changed it takes 1000 series.

  For anything other that a very small number of documents the bitmap index would be deleted and rebuilt after the ETL operations. That is why the data warehouse designs try to minimize update and implement insertions and deletions using partitioning when possible; Adding a new day by adding a new partition.

  There is also a big difference between a bitmap index and a bitmap join index. The white paper you quoted does not really indicate what type are used or recommended.

  Learn more about the difference - see Using Bitmap indexes in data warehouses in the doc of Data Warehousing
  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/indexes.htm

• Index BITMAP Advisor Advisor access SQL on the Partition key

  I ran SQL and SQL Access Advisor as below he recommends index bitmap on p_key... Given that the cust table is partitioned on the p_key, does make sense to create indexes on p_key?
  
  Not sure if SQL Access Advisor look just in ' where clause conditions/predicates "and the cardinality of such columns and not look at whether the table is partitioned or not. T it?
  
  Is it wise to create BITMAP indexes on the partition key? If so what scenario would be beneficial?
  

  SELECT * FROM cust
  WHERE 
      'T' = 'T' AND 
      part_key IN 
      (   2, 3, 4 )) AND 
      (   p_key, act_key) IN ( select p_key, act_key from account where act_type = 'PENDING' and p_key in (2,3,4) )

  user4529833 wrote:
  Jonathan, I have exactly one value per partition for the partition key.   However, most SQLs use 'IN' as predicate of partitioning pruning so overall stats are always used and they are always a bit bland compared to the partition level stats. Then this led SQL Access advisor recommendations?

  Yes, the Counselor also recommended to create Bitmap indexes on act_type... Given this does make sense to have the Bitmap index on the partition key?

  I'll post the execution plan as soon as I have access to the system...

  The fact that statistics are "a little stale" was not much of a difference.

  The fact that Oracle has probably used statistics at the level of the tables is likely to be the underlying issue. Is the partitioned table list or you have rigged it with partitioning range: If you faked list partitioning using partitioning of the range which MAY have contributed to the issue (but it's an assumption that I have not tested).

  Unofficially, the optimizer has said something like:

  + "There are 25 possible values for pkey, there are 4 possible values for act_type, there seems to be 100 different combinations - so your query will pick up X lines. 80% of these lines will be packed in Y blocks and 20% of them will be scattered through the Z blocks if we have two bitmap index, and we will have to do sequential reading of the db file SSS. If we do an analysis through the affected partitions, we do MMM db file scattered reads. What are those cheaper. » +

  You know how false it's - if you know that you need not the pkey index. You also know what is the efficiency of the column act_type is in the identification of data, so you can decide whether or not an index on act_key may be useful.

  Concerning
  Jonathan Lewis
  http://jonathanlewis.WordPress.com
  http://www.jlcomp.demon.co.UK

  "The premature temptation to theories of shape on the lack of data is the scourge of our profession."
  Sherlock Holmes (Sir Arthur Conan Doyle) in "the Valley of fear."

• Question indexing and backup...

  Couple questions.

  1 indexing - I created a directory "backup" off the rooy on my device via the file browser. Even with the pictures etc..., it's the area that I intend to backup just things, documents, programs, etc... To my surprise, images in this directory is indexed and illustrated with photos. Is this by design? In any case stop as long as these are usually the images that go with the product installs.

  2. I noticed in the backup agent it refers to \\myhubname\backup but that folder does not exist (this is why I created it). "However, on this backup operation (the one that installs by default), it stores data to \\myhubname\import\"directory file names "... strange.

  Any thoughts would be appreciated.

  Thank you.

  udflyer

  1. Yes, it's by design. Nothing in the files of importation or the media is indexed. I suggest using the backup folder.

  2. strange that the backup folder was not there. It is a default action.

• Which switch to index for the index bitmap in Oracle Standard Edition

  Hello
  
  I have to move from Oracle Enterprise edition to standard edition (oracle11g). As standard edition does not support bitmap indexes. But the current database which is an Enterprise edition a bitmap index a column-based date or varchar2 or column in a table. The tables have approximately 60000000 records. I would like to know what index go for bitmap index.
  
  
  Kind regards
  Vaibhav
  
  Published by: Vaibhav on November 7, 2011 05:35

  The BTree index certainly can and are frequently used when values are not unique (e.g. are duplicated).

  uniqueness isn't the issue. The relative number of distinct values (relative to the total number of lines) is important. An advantage of BitMap index BTree indexes, it's that BTree indexes can be composite - made up of multiple columns.

  You can read the documentation on the index.

  http://download.Oracle.com/docs/CD/E11882_01/server.112/e25789/indexiot.htm#CBBECABB

  http://download.Oracle.com/docs/CD/E11882_01/server.112/e25494/indexes.htm#i1007132

  Hemant K Collette

• index bitmap and separate key

  Hi guys,.
  
  If the separate keys is very low (for example 20) and my index finger has more than 12,000 lines, should I consider using a bitmap index instead?
  
  Thank you

  OracleGuy777 wrote:
  But that say our table was very fragmented, would not--what it means that the bitmap index entries would be to store much more information than necessary? Say so we had a table with only 1000 entries and the first rowid is 1, and the last was 1000000 and then eventually we have 999000 additional entries for each bitmap index entry!

  Bitmap indexes are well compressed. So, this usually isn't a problem. An example...

  SQL> create table t as select rownum id from dual connect by level <= 1000000;
  
  SQL> execute dbms_stats.gather_table_stats(user,'t')
  
  SQL> select blocks from user_tables where table_name = 'T';
  
      BLOCKS
  ----------
        1557
  
  SQL> delete t where id between 500 and 999500;
  
  999001 rows deleted.
  
  SQL> commit;
  
  SQL> create bitmap index i on t (id);
  
  SQL> select distinct_keys, blevel, leaf_blocks from user_indexes where index_name = 'I';
  
  DISTINCT_KEYS     BLEVEL LEAF_BLOCKS
  ------------- ---------- -----------
            999          1           4
  

  Notice how the index has only 4 blocks of leaves...

  So you're saying something like

  FEMALE 1 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 0 0 0 1

  could be stored as

  FEMALE 1 0 0 0 1 1 0 1 0 1 for rowid a to j
  FEMALE 0 1 1 1 1 0 0 1 0 0 0 1 for rowid k - w

  Yes.

  HTH
  Chris Antognini

  Troubleshooting Oracle, Apress 2008 performance
  http://top.Antognini.ch

• Newbie question (button Bitmap/field/LabelField)

  Hi all

  I am creating a simple application 9700 which has a bitmap (480 * 360) as the image background, title, two separate labels and two buttons (side-by-side) but centered to the base of the form

  Code so far:

  Bitmap borderBitmap = Bitmap.getBitmapResource ("Background.png");
  VerticalFieldManager m = new VerticalFieldManager();
  m.setBorder (BorderFactory.createBitmapBorder (new XYEdges (1,1,1,1), borderBitmap));
        
         
  LabelField lf = new LabelField ("my title here," DrawStyle.HCENTER | ") LabelField.USE_ALL_WIDTH);
  FontFamily fontFamily [] = FontFamily.getFontFamilies ();
  Do police = fontFamily [1].getFont(FontFamily.CBTF_FONT |) Font.BOLD, 40);
  lf.setFont (do);

  LabelField lf1 = new LabelField ("\n1st line of text here.\n\n", DrawStyle.HCENTER: ") LabelField.USE_ALL_WIDTH);
  Police fnt1 = fontFamily [1].getFont(FontFamily.CBTF_FONT |) Font.BOLD, 36);
  LF1. SetFont (fnt1);
         
  Lff LabelField = new LabelField ("second line of text ici\n", DrawStyle.HCENTER: ") LabelField.USE_ALL_WIDTH);
  Police fontFamily = fnt2 [1].getFont(FontFamily.CBTF_FONT |) Font.BOLD, 36);
  lff.setFont (fnt2);
         
  Lf2 LabelField = new LabelField ("\n\n", DrawStyle.HCENTER |) LabelField.USE_ALL_WIDTH);
  Police fnt3 = fontFamily [1].getFont(FontFamily.CBTF_FONT |) Font.BOLD, 36);
  LF1. SetFont (fnt3);
         
  Add (m);
  m.Add (LF);
  m.Add (LF1);
  m.Add (LFF);
  m.Add (LF2);

  BFM HorizontalFieldManager = new HorizontalFieldManager (Manager.HORIZONTAL_SCROLL);
  ButtonField acroos is new ButtonField ("Yes", Field.FIELD_HALIGN_MASK);.
  ButtonField bNo = new ButtonField ("No.", Field.FIELD_HALIGN_MASK);
  BFM. Add (bYes);
  BFM. Add (BNO);
  Add (BFM);

  ------------------------------

  The problem I have is that the basis of the bitmap is missing. The buttons to remain on the left of the dialog box, but the base of the peak is not displayed as the background of the horizontal field Manager is not transparent.

  Click on the button I want to display a dialog box with a label text, which will be just Dialog.Alert ("Some Text");

  How do I change the color of the text of the title, 1 & 2 lines of text, please?

  Also, does anyone have examples of code for a splash screen before loading the dialog box above? I need to have the home screen display a logo which will be 480 * 100 pixels. Have seen an example of a startup but can't seem to get by (too new to the coding).

  Thanks in advance

  To center the buttons at the bottom and let the background show through, try this:

  HorizontalFieldManager bfm = new HorizontalFieldManager(FIELD_HCENTER);
  ButtonField bYes = new ButtonField("Yes");
  ButtonField bNo = new ButtonField("No");
  bfm.add(bYes);
  bfm.add(bNo);
  VerticalFieldManager vfm = new VerticalFieldManager(USE_ALL_WIDTH);
  vfm.add(bfm);
  Background trans = BackgroundFactory.createSolidTransparentBackground(0,0);
  bfm.setBackground(trans);
  vfm.setBackground(trans);
  add(vfm);
  

  To change the color of text, you can use a RichTextField place a LabelField, or you can create a subclass LabelField.

• Bitmap Vs domain of index for large tables

  I have a DB warehouse which consists of very large tables.

  I have two questions:

  1 can I use Bitmap or field type index?

  2. use a different tablespace for storing the indices? This would improve performance?

  Please give me advice to improve the performance of queries for these large tables (more than 300 M record).

  Concerning

  When to use bitmap indexes

  ------------------------------

  -The column has a low cardinality: little separate value

  -Bitmap indexes are particularly useful for complex with ad-hoc queries

  long WHERE clauses or applications of aggregation (containing SUM, COUNT, or other

  aggregate functions)

  -The table contains the number of lines (1,000,000 lines with 10,000 distinct values)

  may be acceptable)

  -There are frequent, possibly ad hoc queries on the table

  -L' environment is focused on the data warehouse (System DSS). Bitmap indexes are

  not ideal for due processing (OLTP) environments transactional online

  their locking behavior. It is not possible to lock a single bitmap.

  The smallest amount of a bitmap that can be locked is a bitmap segment, which

  can be a block of data up to half size. Changing the value of a row results in

  a bitmap segment becomes locked, blocking to force change on a number of lines.

  This is a serious drawback when there are several UPDATE, INSERT or DELETE

  statements made by users. It is not a problem when loading data or

  updated to the stock in bulk, as in data warehouse systems.

  -Bitmap join indexes are a new method of 9.0 by which joins can be avoided in

  pre-creation index bitmap on the join criteria.

  The BJI is an effective way of space reduction in the volume of selected data.

  The data resulting from the join operation and restrictions are

  kept permanently in a BJI. The join condition is a join, equi-internal between the

  column/columns in primary key of the dimension and the foreign key tables

  column or columns in the fact table.

  When to use domain indexes

  ---------------------------------------

  https://docs.Oracle.com/CD/E11882_01/AppDev.112/e41502/adfns_indexes.htm#ADFNS00504

• Index B-Tree VS Bitmap

  Hi all

  I was studying all internal Index and am bit stuck in understanding under point.

  Basically B-Tree and Bitmap uses access ROWID (Root-branch leaves) a row of the table. Now the question is if B-Tree and Bitmap using ROWID to access the value then what is the advantage of using Bitmap indexes on index B-Tree, if column has low cardinality.

  Kind regards

  I was studying all internal Index and am bit stuck in understanding under point.

  The starting point when you are studying is the Oracle documentation.

  Basically B-Tree and Bitmap uses access ROWID (Root-branch leaves) a row of the table. Now the question is if B-Tree and Bitmap use ROWID to access the value then what is the advantage of using Bitmap indexes on index B-Tree, if the column is to have a low cardinality.

  For this issue of language SQL doc and the Data Warehousing Guide answers your question

  http://docs.Oracle.com/CD/B28359_01/server.111/b28286/statements_5011.htm

  BITMAP IMAGE

  Specify BITMAP to indicate that index must be created with a bitmap for each separate key, rather than indexing each line separately. Bitmap indexes store the ROWID associated with a key in the form of bitmap value. Each bit in the bitmap corresponds to a possible rowid. If the bit is set, then it means that the line with the corresponding rowid contains the value of the key. The internal representation of bitmaps is best suited for applications with a low level of concurrent transactions, such as data warehousing.

  That first sentence is the first clue: "a bitmap for each separate key, rather than indexing each line separately. An index of "MALE" (e.g., MALE/FEMALE) bitmap has the AN index entry pointing to "MALE", then a bitmap representing the ROWID for any lines that have the "MASCULINE" attribute

  A lot index is a separate index for EACH line entry. So the difference would pretty much look the same if rows 2,4,6,8,10 are male:

  bunch - "male: 2", "man: 4", "male: 6", "male: 8", "male: 10»

  bitmap - ' male: 2, 4, 6, 8, 10'

  The foregoing is not a faithful but close - image segment index memory is essentially repeat the key value ("male") for each entry, but the bitmap index only indicates "male" once. Oracle can also store this list of ROWID (bitmap) very efficiently and compactly. This saves space and improves the performance.

  The Data Warehousing Guide gives some details:

  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/indexes.htm#sthref85

  Cardinality

  The benefits of using bitmap indexes are the most important for the columns in which the relationship between the number of distinct values for the number of rows in the table is small.

  We refer to this ratio, such as the degree of cardinality. A type column, which has only two distinct values (male and female), is optimal for a bitmap index. However, data warehouse administrators also build indexes on columns with higher cardinalities bitmap.

  For example, on a table with 1 million rows, a column with 10,000 distinct values is a candidate for a bitmap index. A bitmap on this column index can surpass a

  B-tree indexes, especially when this column is often queried in conjunction with other indexed columns. In fact, in a typical data warehouse environments, a bitmap index can be considered for any non-unique column.

  B-tree indexes are most effective for high-cardinality data: that is, for data with several possible values, such as customer_name or phone_number . In a data warehouse, the B-tree indexes should only be used for unique columns or other with very high cardinalities (that is, the columns that are almost unique). The majority of the clues in a data warehouse should be bitmap indexes.

  In ad-hoc queries and similar situations, bitmap indexes can significantly improve query performance. ANDand OR conditions in the WHERE clause of a query can be quickly resolved by performing the corresponding Boolean operations directly on the bitmaps before converting the resulting bitmap to the ROWID. If the number of lines is small, the query can be answered quickly without resorting to a table scan complete.

  As suggested by this text index bitmap can be really powerful when multiple bitmap indexes can be combined to perform AND and OR operations.

  bitmap - ' male: 2, 4, 6, 8, 10'

  bitmap - 'age20': 1,2,5,7,8,9,10'

  It should be easy to see that a predicate of 'MÂLE' OR "AGE20" combine the two bitmaps and produce

  bitmap - ' male | years20 '-1,2,4,5,6,7,8,9,10'

  A string of ROWID values compact nice. Then Oracle can just go GET each of these rows by rowid.

  A predicate of 'MALE' AND 'Years20' would be similar

  bitmap - 'male & years20' - 2,8,10

  Again, YOU, a human, can easily start at the beginning of these 'bitmaps' and select values answering this predicate.

  Just as easily Oracle can combine MUCH these bitmaps at the same time as the ROWID values are SORTED in each group.

• Foglight for Oracle - Bitmap Index

  All,

  Is thre a way for me to detect if an index Dickman is used in a database

  Also, I would be able to tell if a lock is the result of a bitmap index.

  Thank you!

  The index bitmap behave with slightly different locks.  Because of the line are stored in the bitmap, no probable outcome of row in the effective closure of the WHO index of locking.  In the design of applications, you should pay attention when the bitmap indexes are used on tables with updates.

  To find the bitmap indexes, you can use something like

  SELECT INDEX_TYPE, TABLE_OWNER, TABLE_NAME, INDEX_NAME

  OF dba_indexes

  WHERE index_type IN ("BITMAP", "BITMAP AXES on the FUNCTION")

  /

  Conclusion if a lock is being influenced by a bitmap index wouldn't be a combination to find a blocking lock and check if the locked object is a table with a bitmap index.

  The f

• Bitmap index frequently updated useful column or not?

  I have a table of transaction with the status column.

  Table contains millions of records.

  Status, column values can be hold, dealt with, consult, error, completed.

  Initially table column populate status pending and later value will be updated to processed or see even then will be updated to completed or error.

  Is it useful to have the index bitmap on this column we update frequently on the status value

  Is it useful to have the index bitmap on this column we update frequently on the status value

  No - your is NOT a valid use for a bitmap index case.

  There would be little or NO value with only one index of bitmap on the table, if the column has been updated frequently or not.

  The power of the bitmap index is stronger when MULTIPLE indexes are used in the same query to identify/filter data.

  See my answers in this thread

  https://forums.Oracle.com/forums/thread.jspa?MessageID=10217613�

  In this thread I provide more details and code examples and execution of plan that show you a more typical use of bitmap indexes and their power.

  Try this code example to get a better understanding of the proper use of the case for the bitmap index.

• for bitmap or not, that is the question

  Hello my friends tuning.
  
  I'm running Oracle 11.2 (on Solaris 10) for a database very active OLTP, but which is also frequently used to pull reports on the more volatile critical table in the database.
  
  My database has anywhere from 100 to 400 concurrent users.
  Our application (REMEDY) is designed to put 'tickets' in one main table (with about 560 fields that 40 are CLOB).
  The dilemma, I need help is if we put a little map on some low cardinality columns indexes or not.
  And, besides, the number of columns in this table is very low cardinality.
  My fear is that I fear that putting a bitmap on a highly active OLTP table index might decrease the performance of ticket creations (new lines in the table).
  Can or, if I did, I have a job done every night that re-creates the index bitmap on this table?
  But what about performance on the table between the time to rebuild the indexes of BM?
  
  In this case, it is a query that is run on our main table (containing the records of about 6 m and is 16G in size).
  When I look in OEM, I see that he did a scan of full table on this table and in this case, returns only the records of 262.
  Of course, you can deduce that the columns in the predicate clause are very low cardinality (by the names of the columns and the values you want).
  

  SELECT "Main_Ticket"."SHORTTICKETNUMBER"      ,
          "Main_Ticket"."OUTAGESEVERITY"        ,
          "Main_Ticket"."OUTAGESEVERITYTEXT"    ,
          "Main_Ticket"."OUTAGESERVICESLIST"    ,
          "Main_Ticket"."OUTAGESTATUS"          ,
          "Main_Ticket"."OUTAGEOVERALLSTARTTIME",
          "Main_Ticket"."OUTAGEOVERALLENDTIME"  ,
          "Main_Ticket"."CITY"                  ,
          "Main_Ticket"."STATE"                 ,
          "Main_Ticket"."MASTEROUTAGE"          ,
          "Main_Ticket"."GROUPCREATEDBY"        ,
          "Main_Ticket"."GROUPASSIGNEDTO"
  FROM "ARADMIN"."MAIN_TICKET" "Main_Ticket"
  WHERE "Main_Ticket"."OUTAGESEVERITY"<=2
          AND NOT
          (
                  "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'BBSG%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'CIA%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'DESIGNED%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'IHD%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'NABB%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'NCC%'
                  OR "Main_Ticket"."GROUPASSIGNEDTO" LIKE 'NFC%'
          )

  I guess that put the index bitmap on 'OUTAGESEVERITY '.
  Not sure about the GROUPASSIGNEDTO, because it uses the SIMILAR function and may not use the index BM if she had a.
  In this case, an FBI would be better?
  
  Published by: 974632 on February 27, 2013 06:29

  put a bitmap on a table with DML heavy index looks like a very bad idea and I would not even sure if it would help your request (which is the number of values<=2 compared="" to="" the="" total="" number="" of="" rows?="" -="" if="" this="" is="" a="" significant="" amount,="" then="" a="" full="" scan="" is="" propably="" in="" order="" anyway.).="" put="" an="" fbi="" on="" the="" text="" column="" is="" also="" not="" very="" likely="" to="" help="" you="" out,="" especially="" with="" the="" not="" clause.="" it="" would="" be="" much="" easier="" to="" reverse="" the="" logic="" here="" like="" ...="" and="" groupassignedto="" in="" ('group1',="" 'group2'...)="" as="" long="" as="" the="" number="" of="" different="" values="" can="" be="">

  In general, how do you the idea to keep a second copy of this table for reporting? You can create a view, materialized from this table and then create your index bitmap on this MV and run your reports against it. Maybe you could get away with just a drink a day? And the strengthening of this way that you will not lose DML performance against the table real all performance reports. Just an idea

  Bjoern