The difference between index fast full scan and index full scan in Oracle

When the index full scan is made, Oracle navigates to the root block of the index, then to the branch block (if any), then navigates to the first leaf block and then reads it according to the Leaf block's doubly linked list order. The blocks it reads are sequential and sorted.
The index fast full scan is different from the beginning of the segment, reading the containing bitmap block, root block, all the branch block, leaf block, the order of reading is entirely determined by the physical storage location, and take a number of blocks read, each read db_file_ A multiblock_read_count.
So:
1. Index full scan to sort, index fast full scan is not sorted (the index full scan will be returned according to the leaf block sort, and the index fast full scan is returned in the order of storage blocks in the index segment).
2. The index full scan must not read the index segment header, and the index fast full scan to read the index segment header.

The difference between index fast full scan and index full scan in Oracle