RE: null columns and memory?

From: Gogala, Mladen <MGogala_at_allegientsystems.com>
Date: Tue, 27 Sep 2005 17:12:58 -0400
Message-ID: <A2C7821363A0544987988F6BCCE941B506086C@pegasus.lawaudit.com>

The short answer is: no, it isn't correct. The format of the row is this:

|RH|CL|CD|CL|CD|CL|CD....

RH=Row Header, which contains things like ITL entry

CL=Column Length

CD=Column Data

If the column is NULL, then CL=0. There is no "space in memory" reserved for anything.

The explanation of the oracle row format can be found at:

http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14220/schema.h tm#sthref699

Block is brought to memory and stored in buffer cache where it is used for computing

the buffer cache hit ratio, to define how well is your database performing.

Mladen Gogala

Ext. 121

From: ryan_gaffuri_at_comcast.net [mailto:ryan_gaffuri_at_comcast.net] Sent: Tuesday, September 27, 2005 4:15 PM To: oracle-l_at_freelists.org
Subject: null columns and memory?

Someone at work told me the following. Having trouble confirming it in the docs.

If you have a table with a nullable varchar column. If the field is left null no space will be taken up in the database. However, space will be reserved in memory for the column. Is this correct?

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http://www.freelists.org/webpage/oracle-l Received on Tue Sep 27 2005 - 16:13:30 CDT