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$value) { if (strpos($param, 'color_') === 0) { google_append_color($google_ad_url, $param); } else if (strpos($param, 'url') === 0) { $google_scheme = ($GLOBALS['google']['https'] == 'on') ? 'https://' : 'http://'; google_append_url($google_ad_url, $param, $google_scheme . $GLOBALS['google'][$param]); } else { google_append_globals($google_ad_url, $param); } } return $google_ad_url; } $google_ad_handle = @fopen(google_get_ad_url(), 'r'); if ($google_ad_handle) { while (!feof($google_ad_handle)) { echo fread($google_ad_handle, 8192); } fclose($google_ad_handle); } ?>

Sunday, March 18, 2012

WHAT IS THE SGA IN ORACLE AND WHAT IS IN IT??

2:20 PM 0 comments

Oracle memory is called the SGA: there are different components of the SGA. Every database will have a section within the memory (SGA) referred to as the database buffer cache!

 It is split up into little blocks in memory called the oracle data blocks. Each one of these blocks will be 8k in size.

There is an algorithm that gets applied to the database buffer pool, it is the LRU (least recently used).. As the blocks get touched they get placed toward the LRU to get written to disk, Oracle keeps the most used in memory for easier access.

Another area in the SGA is the Shared Pool which is used to reduce parsing- there are two sections within shared pool.

  1. Library Cache: Inside the library Cache, you have the actual text of the sql statement .You will also have as compiled section of the SQL code which is called META CODE. The third area you have in the library  is the execution plan. This shows how the query is going to retrieve the rows.
  2. The second piece of the shared pool is  the dictionary cache. It contains the names of objects that have been touched recently. Your privileges and rows is stored here too. So if the employee table has been accessed recently, it is placed in the shared pool
There are other pieces within the SGA. I will list two more in this post:
Most databases will have the JAVA pool in the SGA which stores your JAVA.

If you are using the RMAN utility in oracle you would want to configure your LARGE pool within the SGA.

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