You use cache tables to store data that you access frequently but
that does not change often.
A cache table can improve query performance by storing the data locally
instead of accessing the data directly from the data source.
You can cache
data from these data sources:
Db2®
family
Informix®
Microsoft SQL
Server
Oracle
Sybase
A cache table consists of these components:
A nickname on your federated database system. The nickname has the same
column definitions and same data access as the data source table.
One or more materialized query tables that you define on the nickname.
The type of materialized query tables is FEDERATED_TOOL maintained materialized
query table. The materialized query table usually contains a subset of high-use
data from the data source table.
A replication schedule for each materialized query table. The replication
schedule keeps the local materialized query tables current with your data
source tables. You define the replication schedule.
The following figure illustrates a cache table.
Figure 1. Cache table.
The cache
table has the same name as the nickname. You can associate a cache table with
only one data source table.
When a cache table is enabled, the query
optimizer directs queries to the cache table if the data that the query requests
can be found in the materialized query table.
