Using Catalog Indirection
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Chapter 3 Performing Additional Installation Tasks 3-19
When you direct the information queries from specific groups of users to a
recent copy of the DB2 catalog, the Administrative Products can reduce
catalog contention. The products also perform better because they do not
have to compete with other applications for DB2 catalog information.
The copy of the catalog can be tuned to improve the performance of the
Administrative Products. If you are using DB2 Version 4 or later, you can
add your own indexes to the copy of the catalog. You can also reorganize the
tables or table spaces of the catalog copy. For information about performance
considerations, see “Performance Considerations” on page 4-2.
For catalog indirection to be effective, you must ensure that the copy of the
catalog reflects the status of the actual catalog. The degree of accuracy that is
required depends on the type of users who are involved and the purpose of
their information queries. The job that updates the catalog copy temporarily
halts all information queries made through the copy.
Controlling Catalog Access
Data centers with highly sensitive information may need to restrict how users
access specific tables in the DB2 catalog. To restrict catalog access, you can
implement catalog indirection through one or more user-created views that
filter out specified columns within the DB2 catalog tables. You can allow
specific user groups to use the Administrative Products in a limited fashion
without compromising the security of the data or data structures that are
defined in the catalog tables.
Considerations for Using a Copy of the Catalog
Maintaining a copy of the catalog uses additional DASD space. The amount
of space that is required equals the size of your DB2 catalog and can vary
greatly, depending on your DB2 system.
For example, assume that a user uses the Administrative Products to perform
an activity that changes information in the DB2 catalog. The user then
completes a task that performs an information query against the copy of the
catalog. In this case, it may seem that the first activity did not succeed.
However, if you implement catalog indirection only for users who are already
restricted to information-only queries, this problem may not occur. For
example, you could implement catalog indirection for those ALTER users
who are not allowed to run the Execution Monitor.
