How Exadata Cell Offloading Works ?

First let's know what is offloading and benefit of cell offloading in Exadata?

What is Cell Offloading :-

It refers to the fact that part of the traditional SQL processing done by the database can be “offloaded” from the database layer to the storage layer.

Benefit: The primary benefit of Offloading is the reduction in the volume of data that must be returned to the database server. This is one of the major bottlenecks of most  large databases.


Below is the example of cell offloading.

We have created table cell_offload with 20 lac records.

#### Checking the cell offloading process in DB parameter  ####


SQL> show parameter cell_offload_processing

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
cell_offload_processing              boolean     TRUE


# Flush buffer_cache and shared_pool to get exact result of offloading scenario #


SQL> alter system flush buffer_cache;

System altered.

SQL>  alter system flush SHARED_POOL;

System altered.


## Disabling Cell_offloading_process and checking the query result ##


SQL> alter session set cell_offload_processing=FALSE;

Session altered.

SQL>set timing on;


SQL> select count(*) from cell_offload where emp_id>2000;

  COUNT(*)
----------
    1998000

Elapsed: 00:02:10.20   


#### Now enabling cell offload process and checking query output ####

SQL> alter system flush buffer_cache;

System altered.

SQL>  alter system flush SHARED_POOL;

System altered.

SQL> alter session set cell_offload_processing=TRUE;

Session altered.

SQL>set timing on;

SQL> select count(*) from cell_offload where emp_id>2000;

  COUNT(*)
----------
    1998000

Elapsed: 00:00:48.75  


Here we can see the huge difference

without Cell offload query took - 00:02:10.20 time
with cell offload it took only 00:00:48.75 time



so here we can conclude that cell offloading is a key part to boost Exadata performance.




You would also like  how Exadata Compression works 

Cheers..!!!!!!!!!!

1 comment:

  1. Excellent man...!!!!
    Keep posting

    ReplyDelete