RE: Index creation and locking

Thanks Ronen. I was creating an index with low cardinality and tried bitmap and explain, but the optimizer wouldn't take the path. So I dropped and recreated it as btree, and the optimizer chose to use it. This behaviour is not consistent with the book. When I have free time, I'll take it up with support.

Table 1M rows, cardinality 3, highly skewed, rows with the value in the where clause=2000. It's a good index for this query.

-----Original Message-----

From: Ronen Levit [mailto:RonenL_at_talmai.com] Sent: Tuesday, August 15, 2000 1:38 AM
To: Multiple recipients of list ORACLE-L Subject: RE: Index creation and locking

Linda,

What I meant in my answer, is that when creating bitmap / btree index, you update the index itself, and there you got the locks I described below.

We've tried to update a bitmap index from few threads and got many locks. Now we're dropping the bitmaps before the process and rebuilding them right after. This is probably the only way to do so. I'm not familiar with any other locks upon creation of index (parallel or not).

Ronen.

-----Original Message-----

Sent: Monday, August 14, 2000 11:05 PM
To: Multiple recipients of list ORACLE-L

Hi Ronen,  

The question was what kind of locks/latches/contentions I could expect at index creation. But thanks just the same.  

Regards,  

Linda

-----Original Message-----

Sent: Monday, August 14, 2000 10:04 AM
To: Multiple recipients of list ORACLE-L

Linda, Lisa,  

Index update locks the row it updates.  

Bitmap indexes though, as they use different mechanism, locks the block it updates, and because the bitmap index holds lots of information in one block, it means lock of large amount of data.  

Bitmap indexes are not good for updates, as they grow in space as well as locking problems. They are intended for data warehousing.  

HTH,   Ronen Levit
Database group manager
Talmai

Tel:  +972 8 9460606 #212 
Fax:  +972 8 9460705 
Cell: +972 52 448699 

-----Original Message-----

Sent: Monday, August 14, 2000 3:00 PM
To: Multiple recipients of list ORACLE-L

Linda,

I have seen this happen with 'resource busy and acquired with nowait specified' error returned to a user trying to query a table while (bitmap) index creation is running. However, it was not consistent.

Heck, try it out and see what you end up with. Let us know.

Lisa

-----Original Message-----

Sent: Friday, August 11, 2000 8:47 PM
To: Multiple recipients of list ORACLE-L

Does index creation lock the underlying records or table for the duration of

the creation, and subsequently interfere with other transactions, such as on-line?

-- 
Author: Linda Hagedorn 
  INET: Linda_at_pets.com 

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