Database slow after Index compute statistics

Question

Dear All,
Since 2 days back after executing Analyze Index compute objects to increase the response time some programs from my application have become very slow.
After seeing this behaviour I went ahead and did a Analyze table compute statistic again . Even after doing this the behaviour has remained the same . Some users have been complaining (becoz the slowness has effected only some tables and not the whole database).
I checked sys.v_$session_longops and got this output
OPNAME      TARGET     ELAPSED_SECONDS
NULL     53     596792483
NULL      53     596793670
¥Á     3248826740 596793669
NULL     53     596793624
NULL     NULL 596800369
NULL     1     596796740
NULL     1732526816     596472777
Table Scan     PO8.ACC_LEDGER      9
Table Scan     PO8.INVENTORY_LEDGER     26
Sort Output     NULL      7
Sort/Merge     NULL      15
Sort/Merge     NULL     66
Table Scan     PO8.INVENTORY_LEDGER     12
Table Scan     PO8.ACC_LEDGER     9
NULL     1725513472     0
NULL     3361240696     0
NULL     3361796632     0
NULL 22     596792484
NULL     1730819772     596800386
NBIAAT56020010ä     (stale) obj# 3363169460     596800605
ýÐ      3506279036     596799303
NULL      NULL     596800634
What could have happened.
In the ini I have set
optimizer mode = Choose
db_file_multiblock_read_count=     8
Sapna

Answer 1

Took a statspack and got these values
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait Ratio: 100.00
Buffer Hit Ratio: 23.70
Library Hit Ratio: 99.52
Redo NoWait Ratio: 99.96
In-memory Sort Ratio: 98.77
Soft Parse Ratio: 98.74
Latch Hit Ratio: 100.00
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
db file scattered read 120,661 0 .00
db file sequential read 26,053 0 .00
SQL*Net more data to client 3,421 0 .00
control file parallel write 314 0 .00
direct path read 244 0 .00
And do you suggest that I do an Analyze table 'table_name' estimate statistics for all the tables.
Sapna