60 Storage Management with DB2 for OS/390
Table17. Examples of SMS Class Usage for DB2 User Databases
6.3 DB2 System D atabases
A DB2 subsystem stores data about itselfwithin a set of tables stored in table
spaces in system databases. The system databases are:
• Catalog database (DSNDB06)
• Directory database (DSNDB01)
• Work database (user defined name or DSNDB07)
DB2 supports a Default database (DSNDB04), which is used when the database
is omitted ina table space or index space creation. The Default databasec anbe
considered a userdatabase and may be handled in the same way as other user
databases. It isnot considered in this section.
The system databases have the same data organization, data type and naming
conventionas user databases. The system databases have stricter availability
requirements. The examplesof SMS classes in Chapter 6.1, “SMS Examples for
DB2 Databases” on page47 are applicable to DB2 system databases.

6.3.1 Catalo g and Directory Databases

The DB2 Catalog andDirector ydatabases contain data definitions, recovery
information, security informationfor the data managed by DB2. If these
databases become unavailable,business data is also unavailable. Recovering
these table spaces is a lengthyand complex process.
Toensure that the availability requirement of the production databases is met,
evenin case of an outage of a DB2 system database, the DB2 Catalog and
Directory databases must have an availabilityrequirement at leas t as stringent as
those of the production database with the highest availabilityrequirement.
Corollary: continuous availabilityof the DB2 Catalog and Directory is required in
order to have continuous availabilityfor a DB2 application.
Databases Performance Availability Migration Storage
Group
OnlineProduction Avg Avg NO SGDB20
Online Production High Avg NO SGDBFAST
Online Production High High NO SGD BCRIT
BatchProduction Low Low YES SGDB21
BatchProduction Good Avg NO SGDB20
BatchProduction High High NO SGDBCRIT
DataWarehouse Low Avg YES SGDB21
DataWarehouse High Good NO SGDBFAST
Development Low Low YES SGDB22
Test Low Low YES SGDBTEST