db file scattered read – oracle wait event

DB File scattered read wait event occurs when an oracle process waits for a physical read of multiple oracle blocks from the disk. This wait identifies that a full scan (Full Table Scan or Index fast full scan) is occurring BUT during this read the blocks are read into memory locations that are not physically…

Index Fast Full Scans

Index Fast Full Scans are similar to Index Full Scans i.e they read index blocks in unsorted order, as they exist on disk.This scan does not use the index to probe the table, but reads the index instead of the table, essentially using the index itself as a table.