Extensive “Full Index Scan” Access Wait

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Index is extensively accessed via full index scans. This is sometimes done to avoid sorts, when the sort order matches the leading portion of the index key, or to avoid accessing table blocks, when all the columns required by the query exist in the index key.

Extensive “Full Index Scan” Access findings

	Description
What to do next	Perform the following: n   Examine associated statements in the Statements tab. n   Focus on the Full Index Scan access type in the Access Types table. n   Examine column usage, for each statement in the Columns table.
Advice	Perform one of the following options: n   Full index scan, can be eliminated by: Identifying common high selectivity columns for the top statements. Create an index matching the statements predicates. Partitioning the table according to the best predicates existing in the statements. n   Full index scan, can be improved by switching to Fast Full Index Scan when the index is not used to save sorts (a fast full scan retrieves the rows according to the index key). Perform one of the following options to enable this access path: Ensure that the Fast_Full_Scan_Enabled parameter = yes. Use the "Index_ffs" hint for major statements that use the full index scan, to check if the fast full scan improves performance. When the full index scan doesn't save sort results, performance may improve considerably.
Example	Table: TAB1 (C1 number, C2 number, C3 number, C10 Date) Index: IX1 (C1) Statement: select C1 from TAB1 Order by C1; Execution plan uses IX1 in Full Index Scan In this case a full index scan is the best option. Because there are no filtering predicates, there is no need to access the table blocks and the sort operation is avoided.

  

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