Control of where simple large object data is stored

A key responsibility of the database server administrator is to control where the database server stores data.

By storing high-use access tables or critical dbspaces (root dbspace, physical log, and logical log) on your fastest disk drive, you can improve performance. By storing critical data on separate physical devices, you ensure that when one of the disks that holds noncritical data fails, the failure affects only the availability of data on that disk.

As the following figure shows, to control the placement of databases or tables, you can use the IN dbspace option of the CREATE DATABASE or CREATE TABLE statements.
Figure 1: Control table placement with the CREATE TABLE... IN statement

This figure shows the following sample SQL: CREATE TABLE stores_demo IN stores_space. This SQL is used to control the placement of the table.

Before you create a database or table in a dbspace, you must first create the dbspace.

A dbspace includes one or more chunks, as the following figure shows. You can add more chunks at any time. A database server administrator must to monitor dbspace chunks for fullness and to anticipate the necessity to allocate more chunks to a dbspace. When a dbspace contains more than one chunk, you cannot specify the chunk in which the data is located.
Figure 2: Dbspaces that link logical and physical units of storage

This figure shows three dbspaces that link logical and physical units of storage. The physical units of storage contain chunks.