Performance issue with a index.

when I run oracle statistics the index still have performance issues. But  I drop and re-create an index. There are no performance issues. That's good. But what is the reason behind this.

I tired to analyze it.

Analyze index PLN_ORD_35 validate structure; and then I do this

SELECT name,height,lf_rows,lf_blks,del_lf_rows FROM INDEX_STATS;

PLN_ORD_35

2

42331

88

0

I don't find anything strange.

My question is how can I found what is the issue is?

Thanks in advance for helping me.

Kind regards,
Santhosh Challa.