Databases Reference
In-Depth Information
DB DBUsed %Used
---------- --------- --------
DWPRD 0.07 0.410
EDW 0.44 2.738
UNKNOWN 0.01 0.051
VISX 7.98 50.211
VISY 7.41 46.588
VISYVISX 0.00 0.001
CachedMB DB HitCount MissCnt objNo
------------- -------- -------- --------- ------------
72.07 VISX 4 1272 3081977
68.11 VISX 0 1875 3037737
66.25 VISX 0 1799 3037737
66.02 VISY 0 1689 3037737
65.68 VISY 4 1124 3081977
To determine the object name for the
objectNumber
column in the rightmost column of the last section above,
query
DBA_OBJECTS
on
DATA_OBJECT_ID
, as outlined in Recipe 18-2.
How It Works
As described in Recipe 18-2, the
flashcachecontent
cell object contains current information about the database
segments stored in Exadata's flash cache. SFC is able to satisfy I/O requests from flash for data stored in flash cache.
The information in the
flashcachecontent
object contains a
cachedSize
attribute, which stores the number of bytes
per
objectNumber
per database.
In this recipe, we provided a simple Perl script that uses
dcli
to fetch
flashcachecontent
data, but you could
also manually retrieve the same information using the following command and sort or format the information to meet
your needs:
$ dcli -g [cell group file] cellcli -e list flashcachecontent attributes \
cachedSize,dbUniqueName,hitCount,missCount,objectNumber
18-4. Determining What Happens When Querying Uncached Data
Problem
You wish to identify what happens when SFC-eligible I/Os are issued and the requested data is not yet available in
flash cache.
Solution
In this recipe, you will learn how to use information from CellCLI's
flashcachecontent
object and flash cache
database statistics to see what happens when an Oracle session issues a request for data
not yet
stored in flash cache.
In this recipe, we present a test in which we query a single row using an index for a table, measure the relevant
statistics, bounce our database, and repeat the test. Our test consists of running the following SQL statement. With
this, we're displaying a portion of the execution plan:
SQL> select customer_id,x.transaction_id from po.rcv_transactions
where transaction_id=2298598;
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