Mysql's auto_increment is how to achieve?

Hello everyone,
I did not find “auto_increment” in the structure of the database table, the primary key will automatically Why growth?
This is how to achieve?

image_pool | CREATE TABLE image_pool (
oid int(11) NOT NULL,
name varchar(128) DEFAULT NULL,
body mediumtext,
uid int(11) DEFAULT NULL,
gid int(11) DEFAULT NULL,
owner_u int(11) DEFAULT NULL,
group_u int(11) DEFAULT NULL,
other_u int(11) DEFAULT NULL,
PRIMARY KEY (oid),
UNIQUE KEY name (name,uid)
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Hi

This is control by the Pool class in oned. Note that the DB is primary used
by OpenNebula to keep its object states; and not as a relational system…