You must have question in your mind that why only two parameters as there are n number of parameters related Exadata and all have it's own importance.
Well, we have choose these two because exadata performance more over dependent on these parameters and major two functionality works on these parameters.
These two parameters are:
_KCFIS_STORAGEIDX_DISABLED
CELL_OFFLOAD_PROCESSING
_KCFIS_STORAGEIDX_DISABLED
- There is not much you can do to control storage index behavior. However, the developers have built in a few hidden parameters that provide some flexibility.
- Above parameter is one of them to control the storage index functionality on exadata.
- This is undocumented and hidden parameter which is used to control the storage index function. It is highly recommended to check with the Oracle support before using it.
- This parameter tells oracle storage if storage index need to be used while performing query execution.
- It is used to enable and disable the usage of storage index when exadata is used for the database.
- By default it is FLASE means storage index is enabled. If you need to disable the usage of storage index than make the value of this parameter TRUE.
Disable storage index:
SQL>alter system set _KCFIS_STORAGEIDX_DISABLED=TRUE;
Enable storage index:
SQL>alter system set _KCFIS_STORAGEIDX_DISABLED=FALSE;
You can also test this on session level.
CELL_OFFLOAD_PROCESSING
- Second parameter is related to the smart scan function of exadata. There are several parameters that apply to offloading.
- The main one is CELL_OFFLOAD_PROCESSING, which turns offloading on and off.
- By default the value of this parameter is TRUE which means smart scan is enabled. In case if you want to test measure the performance of database using or without smart scan , you can use this parameter.
- If it is disabled, it means that predicate filtering and storage indexes cannot be used to cut down the volume of data.
Disable smartscan:
SQL>alter system set CELL_OFFLOAD_PROCESSING=FALSE;
Enable smartscan:
SQL>alter system set CELL_OFFLOAD_PROCESSING=TRUE;
This parameter also can be tested on session level.
