If I am looking at a query plan in Oracle 11g, is there any way I can tell which operations will result in single-block reads and which will result in multi-block?

2 Answers 2


TABLE ACCESS FULL and INDEX FAST FULL SCAN use multi-block I/O, other kind of access paths use single-block I/O.


FULL INDEX SCAN reads the index a block at a time, from start to finish, It uses single-block.

FAST FULL INDEX SCAN reads the entire index, unsorted, as it exists on disk, And use multiblock I/O and read all the leaf, branch, and root blocks.

the same thing happen too in TABLE ACCESS.

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