10053 shows bitmap index not being used - why ?

Hi all,

looking at the tracefile output below:

SINGLE TABLE ACCESS PATH
 COLUMN:    DBE_MTH(CHARACTER)  Col#: 12     Table:
MKER_F_DECKUNGSBEITRAG   Alias: T_DEB
   Size: 7  NDV: 24  Nulls: 0  Density: 1.0015e-08
   Histogram: Freq  #Bkts: 24  UncompBkts: 1497795  EndPtVals: 24
 TABLE: MKER_F_DECKUNGSBEITRAG  Alias: T_DEB
   Original Card: 49926500   Rounded: 2080271  Computed: 2080270.83  Non
Adjusted: 2080270.83
 Access Path: table-scan  Resc:  347730  Resp:  347730
 Access Path: index (skip-scan)
   ss sel 4.1667e-02  andv 2035954
   ss cost 2035954 vs. index scan io cost 16684
   Skip Scan rejected
 Access Path: index (scan)
   Index: MK_IDX_00
   rsc_cpu: 12885810654   rsc_io: 1617892
   ix_sel:  4.1667e-02    ix_sel_with_filters:  4.1667e-02
 Access Path: index (skip-scan)
   ss sel 4.1667e-02  andv 2027407
   ss cost 2027407 vs. index scan io cost 6781
   Skip Scan rejected
 Access Path: index (scan)
   Index: MK_IDX_01
   rsc_cpu: 1731092408   rsc_io: 52339
   ix_sel:  4.1667e-02    ix_sel_with_filters:  4.1667e-02
 Access Path: index (equal)
   Index: MK_BMIDX
   rsc_cpu: 412879   rsc_io: 55
   ix_sel:  4.1667e-02    ix_sel_with_filters:  4.1667e-02
******** Bitmap access path rejected ********
Cost: 334275 Cost_io: 332673 Cost_cpu: 3627695115 Selectivity: 0
Not believed to be index-only.
 BEST_CST: 53103.41  PATH: 4  Degree:  1
Grouping column cardinality [T008_ITN_I]    2
Grouping column cardinality [T130_ACT_R]    561224



Looking at the bitmap index,
 Access Path: index (equal)
   Index: MKER_F_DECKUNGSBEITRAG_BMIDX
   rsc_cpu: 412879   rsc_io: 55

It's got by far the lowest rsc_* values - yet it's not being considered
(Bitmap access path rejected) do these values not show estimated cost ?

What could be the reason ?  Would appreciate someone shedding some light on
this :)

Stefan

Other related posts: