Prev Question
Next Question

Which three are true regarding the use of Storage Indexes?

A.
Different storage regions may have different columns indexed for the same table.

B.
A Storage index is automatically maintained by CELLSRV based on the filter columns of the
offload SQL.

C.
The use of Storage indexes for a particular database can be disabled by using an I/O Resource
Manager Database Plan.

D.
Storage Indexes occupy space in the Smart Flash Cache.

E.
The use of Storage Indexes for particular categories of I/O can be disabled by using an I/O
Resource Manager Category Plan.

F.
A maximum of eight table columns for any table are Indexed per storage region.

Explanation:
F, not D: Each disk in the Exadata storage cell is divided into equal sized pieces called storage
regions (default 1MB). There is an index entry for every storage regions (1MB of data stored on
disk). Each entry contains the minimum and maximum value for columns seen in ‘where’ clause
predicates. Information for up to 8 columns can be stored. The index is then used to eliminate disk
IO by identifying which storage regions don’t match the ‘where’ clause of a query.
Note:
*Storage indexes are used during smart scans. All the limitations to smart scans apply to storage
indexes. They do not work with joins. Bind variables are supported, however it’s slightly more
restrictive than regular indexes/queries.
*The storage index is stored in the memory on each of the Exadata storage cells and is created
and maintained transparently. However, if a storage cell is shutdown or rebooted the storage index
will be lost from memory and will be recreated on subsequent accesses to the data after the cell
has been brought back online.
*Storage Indexes are a very powerful capability provided in Exadata storage that helps avoid I/O
operations. The Exadata Storage Server Software creates and maintains a Storage Index (that is,
metadata about the database objects) in the Exadata cell. The Storage Index keeps track of

minimum and maximum values of columns for tables stored on that cell. When a query specifies a
WHERE clause, but before any I/O is done, the Exadata software examines the Storage Index to
determine if rows with the specified column value exist in the cell by comparing the column value
to the minimum and maximum values maintained in the Storage Index. If the column valueis
outside the minimum and maximum range, scan I/O for that query is avoided. Many SQL
Operations run dramatically faster because large numbers of I/O operations are automatically
replaced by a few lookups. To minimize operational overhead, Storage Indexes are created and
maintained transparently and automatically by the Exadata Storage Server Software.

Prev Question
Next Question

Leave a Reply

Your email address will not be published. Required fields are marked *