db file scattered read

[AK]

Here is a part of trace file . I am finding that oracle is trying to read 8 or 3 or 7 blocks at a time . But block numbers are all sequential i.e. it will read 3 blocks starting from 14706 and then 8 blocks starting from 14710 ( 14706+3 ). Why it doesn't read 8 blcoks always it multi_block_read is set to 8 ? Any Idea . Also what is ela=1 ,does it mean elapsed time is 1 sentisec ?       WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14706 p3=3 WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14710 p3=8 WAIT #32: nam='db file scattered read' ela= 2 p1=4 p2=14718 p3=8 WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14727 p3=3 WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14731 p3=7 WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14739 p3=3 WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14744 p3=8 WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=129784 p3=8     Thanks -ak