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2-108 IBM Informix OnLine Database Server Administrator’s Guide
Create a Database: What Happens on Disk
Each database tblspace entry includes four components:
■ Database name
■ Database owner
■ Date and time the database was created
■ The tblspace number of the systables system catalog table for this
database
The database tblspace includes a unique index on the database name to
ensure that every database is uniquely named. For any database, the
systables table describes each permanent table in the database. Therefore, the
database tblspace only points to the detailed database information located
elsewhere. When the root dbspace is initialized, the database tblspace first
extent is allocated. The initial extent size and the next extent size for the
database tblspace are four pages. You cannot modify these values.
Create a Database: What Happens on Disk
After the root dbspace exists, users can create a database. The SQL statement
CREATE DATABASE allows users to specify the dbspace where the database is
to reside. This dbspace is the location for the database system catalog tables
and all data and corresponding index information. (Blob data can be stored
in a separate blobspace.)
By default, the database is created in the root dbspace. Users can place the
database in another dbspace by specifying the dbspace name in the CREATE
DATABASE
statement.
The paragraphs that follow describe the major events that occur on disk
when OnLine adds a new database.