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|V$SQL||IO_CELL_OFFLOAD_ELIGIBLE_BYTES||Number of eligible bytes for offload processing. If column shows 0 (zero), it means the statement was not off-loadable.|
|V$SQL||IO_INTERCONNECT_BYTES||Number of bytes exchanged between compute nodes and Exadata cells|
|V$SQL||IO_CELL_UNCOMPRESSED_BYTES||Number of uncompressed bytes that are offloaded to/from Exadata cells|
|V$SQL||IO_CELL_OFFLOAD_RETURNED_BYTES||Number of bytes returned by Exadata cells from Smart Scan processing|
|DBA_HIST_SQLSTAT||IO_OFFLOAD_ELIG_BYTES_TOTAL||Total number off offload-eligible bytes for SQL_ID across all samples|
|DBA_HIST_SQLSTAT||IO_OFFLOAD_ELIG_BYTES_DELTA||Total number off offload-eligible bytes for SQL_ID between current sample and previous sample|
|DBA_HIST_SQLSTAT||IO_INTERCONNECT_BYTES_TOTAL||Total number off bytes exchanged between compute nodes and Exadata cells across all AWR samples|
|DBA_HIST_SQLSTAT||IO_INTERCONNECT_BYTES_TOTAL||Total number off bytes exchanged between compute nodes and Exadata cells between current sample and previous sample|
|DBA_HIST_SQLSTAT||IO_OFFLOAD_RETURNED_BYTES_TOTAL||Number of bytes returned by Exadata cells from Smart Scan processing across all samples|
|DBA_HIST_SQLSTAT||IO_OFFLOAD_RETURNED_BYTES_DELTA||Number of bytes returned by Exadata cells from Smart Scan processing for current sample.|
Let’s test things with the SOE.ORDERS table from the SwingBench order management load test generator. First, we’ll mark all indices on SOE.ORDERS invisible so we can have our test not eligible for Smart Scan processing:
Now we’ll run a test with cell_offload_processing set to false via a SQL statement hint as well as a comment in the SQL statement so we can retrieve with sql_offload.sql. After this, we’ll run a test with offload processing enabled.
The results above show this:
One interesting thing to note has to do with execution plan display when cell_offload_plan_display is set to AUTO or ALWAYS. As stated previously in this document, if the table/segment resides on an Exadata cell, the execution plan will show “ACCESS STORAGE” clauses whether or not it actually was offloaded or not. See below:
To determine whether your SQL statement benefitted from Smart Scan cell offload functionality in Exadata environments, you can check V$SQL, V$SESSTAT, and V$MYSTAT.
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