ROWNUM is indexed in the Fact table - How to optimize performace with this?

Question

Hi,
I have a scenario where there is an index on the Rownum.
The main Fact table is partitioned based on the job number (Daily and monthly). As there can be multiple entries for a single jobID, the primary key is made up of the Job ID and the Rownum
This fact table in turn is joined with another fact table based on this job number and rownum. This second fact table is also partitioned on job ID.
I have few reference tables that are joined with the first fact table with btree index.
Though in a normal DW scenario we should use bitmap, here we can't do that as lot of other applications are accessing data (DML queries) where bitmap will be slow. So I am using STAR_TRANSFORMATION hint to use the normal index as bitmap index.
Till here it is fine. Problem is when I simply do a count for a specific partition from a reference table and a fact table, it is using all required indexes as bitmap with very low cost. But also it is using ROWNUM index that is of very very high cost.
I am relatively new to Oracle tuning. I am not able to understand what it is exactly doing. Could you please suggest if I can get rid of this ROWNUM to make my query performance faster? This index can not be dropped. Is there a way in the hint I can instruct not to use this primary key index?
Or Even by using is there a way that the performance will be faster?
I will highly appreciate any help in this regard.
Regards
...

Answer 1

Just sending the portion having info on the partition and Primary index as the entire script is too big.
CREATE TABLE FACT_TABLE
JOBID VARCHAR2(10 BYTE) DEFAULT '00000000' NOT NULL,
RECID VARCHAR2(18 BYTE) DEFAULT '000000000000000000' NOT NULL,
REP_DATE VARCHAR2(8 BYTE) DEFAULT '00000000' NOT NULL,
LOCATION VARCHAR2(4 BYTE) DEFAULT ' ' NOT NULL,
FUNCTION VARCHAR2(6 BYTE) DEFAULT ' ' NOT NULL,
AMT.....................................................................................
TABLESPACE PSAPPOD
PCTUSED 0
PCTFREE 10
INITRANS 11
MAXTRANS 255
STORAGE (
INITIAL 32248K
LOGGING
PARTITION BY RANGE (JOBID)
PARTITION FACT_TABLE_1110500 VALUES LESS THAN ('01110600')
LOGGING
NOCOMPRESS
TABLESPACE PSAPFACTTABLED
PCTFREE 10
INITRANS 11
MAXTRANS 255
STORAGE (
INITIAL 32248K
MINEXTENTS 1
MAXEXTENTS 2147483645
BUFFER_POOL DEFAULT
PARTITION FACT_TABLE_1191800 VALUES LESS THAN ('0119190000')
LOGGING
NOCOMPRESS
TABLESPACE PSAPFACTTABLED
PCTFREE 10
INITRANS 11
MAXTRANS 255
CREATE UNIQUE INDEX "FACT_TABLE~0" ON FACT_TABLE
(JOBID, RECID)
TABLESPACE PSAPFACT_TABLEI
INITRANS 2
MAXTRANS 255
LOCAL (
PARTITION FACT_TABLE_11105
LOGGING
NOCOMPRESS
TABLESPACE PSAPFACT_TABLEI
PCTFREE 10
INITRANS 2
MAXTRANS 255
STORAGE (
INITIAL 64K
MINEXTENTS 1
MAXEXTENTS 2147483645
BUFFER_POOL DEFAULT
......................................................