Does dropping bitmap index and creation of b- index cause any dead locks

Does dropping a bitmap index on table which is being used continuously for DML operations and creation of b- index cause any dead locks on a table
in oracle 10g database
( 10.1.0.4.0 - 64bi).
we have seen alert log file which has dead lock occurrence.. would index change/re-creation resulted dead lock or some other reason?
Could you please give us info or help us on this.. thanks in advance..

Bitmap indexes can be the cause of deadlocks on busy systems.
Dropping indexes may cause some locking.
Creating indexes may cause some locking.
You haven't given any traces or scripts or lock information, so difficult to say which one (if any) was the cause of your deadlocks.
It would be better to do this activity when the system is not busy.

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Which index I should create Btree or Bitmap index?

I have table with columns c1,c2,c3
I want to create index on column c1
which index I should create Btree or Bitmap index
the column contain 50% unique values and 50% duplicate values
If Btree why?
If Bitmap Why?
I know that
Btree is used when there more unique values (high cardinality)
Bitmap is used when there less unique values (low cardinality)

read this -
Deadlocks with Bitmap Indexes
Bitmap indexes were designed to be used solely within data warehouses, i.e. where the vast majority of the database activity is reading data,
and there's very little (or no) data modification, except for batch processes which occasionally re-populate the warehouse.
Each "row" in the bitmap index contains references to potentially many different rowids, in contrast to a B*-tree index which references a single rowid.
It should be obvious, therefore, that, since the transactional mechanism is the same for all database operations, that any DML on a table which impacts the bitmap index may end up locking (or attempting to lock) many different "rows" within the index.
This is the key concept with deadlocks in bitmap indexes, you're not being deadlocked on the underlying table, but on the index blocks. Courtesy - http://www.oratechinfo.co.uk/deadlocks.html
hope u got it now...

Bitmap index column goes for full table scan

Hi all,
Database : 10g R2
OS : Windows xp
my select query is :
SELECT tran_id, city_id, valid_records
FROM transaction_details
WHERE type_id=101;
And the Explain Plan is :
Plan
SELECT STATEMENT ALL_ROWSCost: 29 Bytes: 8,876 Cardinality: 634
1 TABLE ACCESS FULL TABLE TRANSACTION_DETAILS** Cost: 29 Bytes: 8,876 Cardinality: 634
total number of rows in the table = 1800 ;
distinct value of type_ids are 101,102,103
so i created a bit map index on it.
CREATE BITMAP INDEX btmp_typeid ON transaction_details
(type_id)
LOGGING
NOPARALLEL;
after creating the index, the explain plan shows the same. why it goes for full table scan?.
Kindly share ur idea on this.
Edited by: 887268 on Apr 3, 2013 11:01 PM
Edited by: 887268 on Apr 3, 2013 11:02 PM

>
I am sorry for being ignorant, can you please cite any scenario of locking due to bitmap indices? A link can be useful as well.
>
See my full reply in this thread
Bitmap index for FKs on Fact tables
>
ETL is affected because DML operations (INSERT/UPDATE/DELETE) on tables with bitmapped indexes can have serious performance issues due to the serialization involved. Updating a single bit-mapped column value (e.g. from 'M' to 'F' for gender) requires both bitmapped index blocks to be locked until the update is complete. A bitmap index stored ROWID ranges (min rowid - max rowid) than can span many, many records. The entire 'range' of rowids is locked in order to change just one value.
To change from 'M' the 'M' rowid range for that one row is locked and the ROWID must be removed from the range byt clearing the bit. To change to 'F' the 'F' rowid id range needs to be found, locked and the bit set that corresponds to that rowid. No other rows with rowids in the range can be changed since this is a serial operation. If the range includes 1000 rows and they all need changed it takes 1000 serial operations.

Issue in dropping an index when doing Online Index drop and Creation

Hi All,
We have done an implementation, wherein, we are creating Online indexes and dropping them when we have a new Release, and a new build. What we do is, we take the difference in existing DB indexes and the ones present in our script, and then a script is executed which drops/modifies/creates new index.
However, what is happening is when we are carrying out some activity in our application, the script tries
to drop an index and fails with "Resource Busy and acquire with NOWAIT."
Any ideas how to handle this situation. Or should we segregate dropping of old indexes and creation of new indexes?

cause for this problem:
Resource Busy and acquire with NOWAIT:
Whenever you try to do any structural changes on a table oracle try to lock the table exclusively with NOWAIT option(this is in 10.2g while in 11g you can change the wait timeout). If oracle fails to lock the table exclusively then ORA-00054 will occur.
Solution for this: (try this link)
http://arjudba.blogspot.com/2009/01/ora-00054-resource-busy-and-acquire.html
http://oracle-error.blogspot.com/2008/10/ora-00054-resource-busy-and-acquire.html
RSD

Refreshing Materialized View and (Bitmap) indexes

In my data warehouse I have an MV that is re-built every night.
1. Initially it was fully refreshed, but dropping and re-creating was shown to be quicker as a general rule
2. It was sometimes sensitive to changes in the underlying objects
3. Its has union alls in it so is complex
It has 6 indexes (4 bitmap and 2 b-tree) built on it which take between 8 and 20 minutes each to create. I would like to reduce this time. I'm already doing the index creation as parallel jobs.
I can re-organise the underlying tables so that the MV is no longer complex, and put an MV log on, to enable a fast refresh. Then, ideally, the indexes can be permanent But I know that bitmap indexes don't like certain changes (they can multiply in size an become unusable). Does this include refreshes of MVs? If it does I might be able to switch to b-tree indexes as our report performance is well within the allowable window, unlike my nightly ETL.
The MV has 160M rows in it and the rate of change is rarely more than 1%/day
I'm on 9i

<Initially it was fully refreshed, but dropping and re-creating was shown to be quicker as a general rule >
Huh? I wouldn't think that a drop and recreate would be any faster, but won't argue with your results. I assume the same events happen for both and take the same amount of time, with the drop/refresh promoting fragmentation.
< It was sometimes sensitive to changes in the underlying objects >
Yup. All kinds of views are, even real ones. I've found that on 10g MVs are also very tempermental
< Simplest answer from me is that I will go for a fast refresh with MV logs. >
I'm not sure you can fast refresh a query with UNIONS. There's a list of restrictions for fast refreshes that's so long I can't keep track of all the rules.
< would you drop and recreate the bitmp indexes either side of the fast refresh? >
If you're doing a fast refresh you shoud not need to.
You might also consider using the NOLOGGING option on index dropping recreation, used to turn archivel logging off. Since you won't be restoring a failed index creation in case of database failure anyway it should be fairly safe.
Also, when creating the bitmaps make sure you're allocating enough memory to the process. Check your initialization/session parameters, particularly the ones pertianing to bitmap indexes.
Message was edited by:
riedelme

How does OWB deal with bitmap indexes when inserting?

How does OWB 9.2 deal with bitmap indexes on a fact table when records are inserted from a staging table? It seems to me that they are left on the table, while in the 9i Server manuals it says that one should not perform heavy DML in this case, because this slows down the inserts considerably and the indexes can get bloated. Should one define a premapping and postmapping process for removal and recreation of the bitmap indexes?
How handles OWB bitmap indexes in case of PEL and what action should one take then?
Jaap.

Hai Japp,
It depends on the volume of the data.
The best way is drop index in pre mapping process and recreate it in post mapping process.
You need to use EXECUTE IMMEDIATE command in the procedure to create or drop indexes.
e.g:
EXECUTE IMMEDIATE 'CREATE BITMAP INDEX INDX_BI_TABLE ON TABLE_NAME(COL_NAME)'
Regards,
Malli

Bitmap index and group by queries

Please could someone offer me some advice for a data warehouse table I am designing which will have ad hoc queries running against it mainly grouping by day/month/year and needs to use as little resources as possible.
TRANS_DATE DATE, LOC_ID VARCHAR2(8), USER_ID VARCHAR2(8), TRANS_CODE VARCHAR2(3), COUNT NUMBER(8,0)
In populating the table I truncated the trans_date to hourly data and aggregated the other columns to give me an hourly count for every combination of location, user and code. I wasn't sure if I should create 2 more columns with truncated dates by day and by month? There are 200,000 rows per day in this table.
The first 4 columns have low cardinality so I decided to create Bitmap indexes on them. However, when querying in Application Express SQL Workshop and looking at the query plan it seems that a full table scan is being performed whenever I use a group_by(example below), even when i use a hint for the index. The bitmap index is used on simple select queries with where clauses but no grouping.
SELECT LOC_ID, count(TOTAL)
FROM TRANS_SUMMARY
GROUP BY LOC_ID
Am I doing this the right way? Or would multiple materialised views / btree indexes be a better way of ensuring fast group_by queries on this table?
Thanks in advance.
Paul

You don't need a separate materialized view for every combination. You may need a few carefully chosen combinations, in addition to appropriate dimensions for rollups.
For example, a materialized view that aggregated dat based on location_id, trans_code, and hour could be used to aggregate by location_id, trans_code and day (i.e. adding up 24 rows from the MV for each trans_code and location_id) or location_id, trans_code and month (i.e. adding 24*30 rows from the MV for each trans_code and location_id). The more rows you have to aggregate, and the more frequently the higher level aggregates are accessed, the more likely you'd want to have a separate MV that aggregates at the higher level (i.e. if you're accessing monthly summary data totals all the time).
If you are rarely aggregating by trans_code, and you have lots of different trans_code values, you could use the one MV that aggregated by location_id, trans_code, and hour to do a monthly aggregate just on location_id and month, but that requires adding 24*30*# trans_code rows from the MV, which may be expensive. It may make sense to have a separate MV for that, or a set of MV's that are aggregated just by location_id and day, or some combination.
Justin

BW, BRTools, statistics, monitoring and bitmap indexes.

Hi all, I have a question about the above.
Oracle 10.2, Solaris 10, BW 7.00
We have a script that generates statistics weekly on our systems. lately, I have been noticing the following messages in the output after the BRTools statistics job is run:
BR0988W Bitmap index "Index_name" selected for checking statistics - please activate the monitoring attribute for table "Table_name"***
After reading SAPNotes 442395, 588688 & 408527, doing searches of SAPNotes, this forum and other forums such as ITToolbox, the answer to the above is "activate monitoring for the above/all tables". I get this.
My issue is that after seeing warnings or missing/skipped statistics, I will manually run the following
brconnect -u / -c -f stats -t all -p 4 as the SID_ORA user
When I do that, the warning message (BR0988W) does not appear in the output. And if I check the table in Oracle with something like the following:
select tablespace_name, table_name, partitioned, monitoring from all_tables where table_name = '"Table_name"';
The ouput is
TABLESPACE_NAME TABLE_NAME PAR MON
"Tablespace_name" "Table_name" YES YES
which shows that monitoring is activated for the table.
My question is, by running "brconnect -u / -c -f stats -t all -p 4" was monitoring turned on? This would mean that I would not have to run the script suggested in 408527. Or can the BR0988W error be generated even though monitoring is activated.
The next time I see the error in the statistics output, I will run the SQL and check the status of the table before running the BRTools stats update.
Table_name and Index_name are just generic markers. I have checked and confirmed that I have not mistyped actual names when running select statements.

As far as i know this message is outdated with 10g.
Please have a look at this discussion: DB13 - Update Sttats - activate the monitoring attribute for table
Cheers Michael

Diff b/w btree and bitmap index ?

What is the difference between btree and bitmap index ?
which one to used and when.
how they are differ from each other.

you'd love to see
http://www.oracle.com/technology/pub/articles/sharma_indexes.html

Buffering and creation of secondary indexes.

Hi All,
I have a table that has more than 6 million records, due to which performance is slow during the transaction search, kindly let me know if Buffering and creation of secondary indexes will help me.
I am given to understand that creation of seconary indexes and full buffering may not always improve performance. Kindly let me know when it is advised to go for full buffering.
Regards,
Thiru

Hi,
create secondary index for the table
check below link
http://help.sap.com/saphelp_nw70/helpdata/en/cf/21eb20446011d189700000e8322d00/content.htm
Regards,
Madhu

Bitmap Index Not Used in PROD and used in DEV

I am in a situation where in in DEV Bitmap Index is used and in PROD bitmap Index is not used. I checked the count, in PROD I have 10 mil rows and in DEV I have 16 mil rows. Optimizer is CHOOSE and also when I tried to force to use index in PROD, I got higher cost.
Any suggestions why Index is not used in PROD as opposed to DEV

As other says, no guarantee that the same query with same setting OS, ORACLE to produce the same execution plan. Also, as Justin said, dont every take cost as your tuning parameter, pay attention to response time, also, number of logical reads and physical reads. What are the wait events during?
For an index, most important factors are, blevel, clustering_factor, number of distinct values. Clustering actor make a lot of difference. You said, when you force index to use, your performance has gained. If so, why not, why the HINTS there in place? Go ahed and use it, but, after all the R&D. Are the Optimizer* paraemters same on the both databases?
If possible, post the execution plan of the query, with HINT and without HINT as well.
Jaffar

Bitmap indexes and group by

I'm trying to understand why Oracle 8.1.6 sometimes uses bitmap indexes sometimes not.
Of course I have all the statistics, my bitmap indexes are valid and so on.
The problem is this:
- I have a customer table very very large
- I have many columns with bitmap indexes
- I run this statement:
select education_key, count(*)
from customer
group by education_key
and obtain a correct execution plan:
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=235 Card=5 Bytes=10)
1 0 SORT (GROUP BY NOSORT) (Cost=235 Card=5 Bytes=10)
2 1 BITMAP CONVERSION (COUNT)
3 2 BITMAP INDEX (FULL SCAN) OF 'CL_EDU'
with the use of the bitmap indexes (only five different values)
- now I want to put a condition on a column
which has a bitmap index.
The new statement is:
select education_key, count(*)
from customer
where age_key = 30
group by education_key
No join, only a scan of a sort of
fact table. In this case Oracle
doesn't use the bitmap index on
education_key:
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=3458 Card=5 Bytes=20
1 0 SORT (GROUP BY) (Cost=3458 Card=5 Bytes=20)
2 1 TABLE ACCESS (BY INDEX ROWID) OF 'CUSTOMER' (Cost=3395 C
ard=18296 Bytes=73184)
3 2 BITMAP CONVERSION (TO ROWIDS)
4 3 BITMAP INDEX (SINGLE VALUE) OF 'CL_AGE'
With this execution plan Oracle has to
read some blocks from the table when I
think that using both the bitmap indexes
the query is faster.
Someone knows why Oracle has this
behaviour? I'm trying to change
many things (also altering statistics
value), but it seems that with a
condition Oracle doesn'use the bitmap
index on the group by column.
null

Hi Michael, what is the address for the lasagne? ....
In init.ora.parms I had 32Mb for bitmap index merge, I suppose it's enough, hovewer I have tried to increase it and nothing changes.
I already use STAR_TRASFORMATION_ENABLED=TRUE.
I have tried with different level of statistics (estimate, compute, also with very precise histograms), always the same
behaviour. I have also tried to change, in a manual way, the statistics in order to change the Oracle behaviour but nothing ...
For this particular statement even if I use the INDEX_COMBINE hint, I mantain the same execution plan.
I use CHOOSE, FIRST_ROWS, ALL_ROWS: always the same behaviour.
I think that Oracle is not able to use a bitmap index on a column involved in a group by when there is another condition in the select.
Hovewer with bitmap indexes, I have many other problems (to read 1% of the table Oracle decides to make a full table scan even if there are the correct bitmap indexes ...).
Many of them are solved using BITMAP_INDEX, but it's difficult to use it in a query tool like Discover or Business Objects because I have to fix the use of INDEX_COMBINE also in situation in which this use is not correct from a performance point of view.
The life with the query optimizer is very hard!
Thank you for your guesses

Bitmap indexes have effect on query execution and equation of values.

Hi,
I have a Fact table and 17 dimension tables linked to it. On each foreign-key in the Fact-Table I have created a BITMAP Index. After that I Analyzed the fact table and made sure that the referential constraints were valid.
Everything seem to be OK until I ran into a difference in totals when using the next 2 queries that should both result into the same total amount.
Query 1:
Below query is resulting in a wrong total amount and seems to be cartesian.
SELECT    SUM(F.DOLLARS)
FROM       SALES_FACTS         F
,               DIM_TIME                A
,               DIM_CUSTOMER      B
,               DIM_SALESAGENT C
,               DIM_SALESTYPE     D
,               DIM_GEOGRAFIC     E
WHERE    F.TIME_ID     =     A.TIME_ID
AND         F.CUST_ID     =    B.CUST_ID
AND         F.SA_ID         =    C.SA_ID
AND         F.ST_ID          =   D.ST_ID
AND         F.GEO_ID       =   E.GEO_ID
AND         A.YEAR          =   '2006'
AND         C.SALESNUM =   '3770'
AND D.ST_ID <> '4'
Query 2:
Qeury 2 is the same as query 1 exept the the type of sales (D.ST_ID) is now set with in a range of allowed values. This query gives the correct result.
SELECT    SUM(F.DOLLARS)
FROM       SALES_FACTS         F
,               DIM_TIME                A
,               DIM_CUSTOMER      B
,               DIM_SALESAGENT C
,               DIM_SALESTYPE     D
,               DIM_GEOGRAFIC     E
WHERE    F.TIME_ID     =     A.TIME_ID
AND         F.CUST_ID     =    B.CUST_ID
AND         F.SA_ID         =    C.SA_ID
AND         F.ST_ID          =   D.ST_ID
AND         F.GEO_ID       =   E.GEO_ID
AND         A.YEAR          =   '2006'
AND         C.SALESNUM =   '3770'
AND D.ST_ID in ('1','2','3','5') In my situation it seems that when I use the <> (not equal to) symbols in combination with the bitmap indexes, that the result of the sum becomes cartesian and thus incorrect.
Has anyone an idea why the calculation of the total amount is different in both queries?
Any help is very appreciated.
Regards, Ilona

Another strange effect is when I leave out the quotation around the not equal to 4 for the Sales_type id (ST_ID <> 4 in stead op ST_ID <> '4' ) then the totals is perfect.
Query 1 version without quotations around ST_ID:
SELECT    SUM(F.DOLLARS)
FROM       SALES_FACTS         F
,               DIM_TIME                A
,               DIM_CUSTOMER      B
,               DIM_SALESAGENT C
,               DIM_SALESTYPE     D
,               DIM_GEOGRAFIC     E
WHERE    F.TIME_ID     =     A.TIME_ID
AND         F.CUST_ID     =    B.CUST_ID
AND         F.SA_ID         =    C.SA_ID
AND         F.ST_ID          =   D.ST_ID
AND         F.GEO_ID       =   E.GEO_ID
AND         A.YEAR          =   '2006'
AND         C.SALESNUM =   '3770'
AND D.ST_ID <> 4 I still have no clue what causes this effect.
Regards, Ilona

Does dropping bitmap index and creation of b- index cause any dead locks

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