Effect of bitmap indices on inserts

Question

Hi,
I have a table where the are 6 indices out of which 4 are bitmap. The table consist of a 110 million records.
-- When I am inserting records in my table how is the presence of the bitmap index going to affect the performance
of my insert statements.
-- Do I need to drop and recreate my indices? If yes do I need to drop all indices or only the bitmap ones.?
-- Also if during an insert the columns on which the index(particularly bitmap) is created is NOT referred then will it
still affect the perforamnce of the insert statements.?
Wolud appreciate your help.
Thanx...

Answer 1

That is not correct. The thing you lock is a single index entry - and there may be multiple index entries for the bitmap on "MARRIED". Your statement might be true for a fairly small table, but that's a coincidence and not design.Session 1
==========
DWDEVDB$SYS> create table test (id number, name varchar2(2));
Table created.
DWDEVDB$SYS> create bitmap index test_idx on test(id);
Index created.
DWDEVDB$SYS> insert into test values(1,'a');
1 row created.
DWDEVDB$SYS> insert into test values(1,'b');
1 row created.
DWDEVDB$SYS> insert into test values(1,'c');
1 row created.
DWDEVDB$SYS> insert into test values(1,'d');
1 row created.
DWDEVDB$SYS> insert into test values(2,'e');
1 row created.
DWDEVDB$SYS> insert into test values(2,'f');
1 row created.
DWDEVDB$SYS> insert into test values(2,'g');
1 row created.
DWDEVDB$SYS> insert into test values(2,'h');
1 row created.
DWDEVDB$SYS> commit;
Commit complete.
DWDEVDB$SYS> insert into test values(2,'i');
1 row created.
DWDEVDB$SYS> insert into test select * from test;
8 rows created.
DWDEVDB$SYS> insert into test select * from test;
16 rows created.
DWDEVDB$SYS> insert into test select * from test;
32 rows created.
DWDEVDB$SYS> insert into test select * from test;
64 rows created.
DWDEVDB$SYS> insert into test select * from test;
128 rows created.
DWDEVDB$SYS> insert into test select * from test;
256 rows created.
DWDEVDB$SYS> insert into test select * from test;
512 rows created.
DWDEVDB$SYS> insert into test select * from test;
1024 rows created.
DWDEVDB$SYS> insert into test select * from test;
2048 rows created.
DWDEVDB$SYS> insert into test select * from test;
4096 rows created.
DWDEVDB$SYS> insert into test select * from test;
8192 rows created.
DWDEVDB$SYS> insert into test select * from test;
16384 rows created.
DWDEVDB$SYS> insert into test select * from test;
32768 rows created.
DWDEVDB$SYS> insert into test select * from test;
65536 rows created.
DWDEVDB$SYS> insert into test select * from test;
131072 rows created.
DWDEVDB$SYS> commit;
Commit complete.
DWDEVDB$SYS> insert into test values(2,'Z');
1 row created.
----------------------Now go to session 2
DWDEVDB$SYS>Session 2
==========
DWDEVDB$SYS> update test set name='T' where name='e' and id=2;
1 row created.
32768 rows updated.
------------Update did not hang here even though it is updating a row with id=2 becuase rows being affected here might not be in the segment which is locked by the first session.
DWDEVDB$SYS> insert into test values(2,'y');
----------------It hangs here because now it is inserting values in a bitmap segment which is alreay locked by the first session because first session is also locking probably last bitmap segment and same segment is being tried to be locked by this sessionSalman