RE: null columns and memory?
- From: "Gogala, Mladen" <MGogala@xxxxxxxxxxxxxxxxxxxx>
- To: "'ryan_gaffuri@xxxxxxxxxxx'" <ryan_gaffuri@xxxxxxxxxxx>, oracle-l@xxxxxxxxxxxxx
- Date: Tue, 27 Sep 2005 17:12:58 -0400
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@xxxxxxxxxxx [mailto:ryan_gaffuri@xxxxxxxxxxx]
Sent: Tuesday, September 27, 2005 4:15 PM
To: oracle-l@xxxxxxxxxxxxx
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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