Why can the explain plan be different from 2 exact set of structures

hi,
i have from a view some base tables let's say A , B, C & D
this query is running very slow . so from the same database , i created tables A1 , B1, C1,& D1 from the above tables.
i created some new indexes on A1 to D1 tables and the results returned to me is fast.
i did an exlain plan
so i drop the indexes on the original A to D table and created the new indexes as per A1 to D1 and analyzed them. and i also did an explain plan
but the query is still running slow and also the explain plan is different to the one from A1 to D1 (the one that running fast)
pls help me to understand how/why can this happen ?
tks & rdgs

hi,
precisely i could have been providing insufficient information but i am too inexperienced to be able to give you the required information and i am also not very sure where i could get the info so that you all can advise me further.
but this is from the user_tables , the only difference i see is that
under LOGGING table A to E is 'YES'
TABLE_NAME     TABLESPACE_NAME     PCT_FREE     LOGGING     BACKED_UP     NUM_ROWS     BLOCKS     CACHE     TABLE_LOCK     PARTITIONED
A1          OWNER1          10          NO          N     37332          883         N     ENABLED     NO
B1          OWNER1          10          NO          N     43458          861         N     ENABLED     NO
C1          OWNER1          10          NO          N     823828          7826         N     ENABLED     NO
D1          OWNER1          10          NO          N     881176          14646         N     ENABLED     NO
E1          OWNER1          10          NO          N     18868          223         N     ENABLED     NO
A          OWNER1          10          YES          N     37040          880         N     ENABLED     NO
B          OWNER1          10          YES          N     43386          880         N     ENABLED     NO
C          OWNER1          10          YES          N     823820          7684         N     ENABLED     NO
D          OWNER1          50          YES          N     880948          26624         N     ENABLED     NO
E          OWNER1          10          YES          N     18690          244         N     ENABLED     NOtks & rdgs

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[email protected] wrote:
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