There are a number of system tables and views provided by Oracle which is really all that the Enterprise Manager uses. You can use USER_TABLESPACES or DBA_TABLESPACES for tablespace info, USER_TABLES or DBA_TABLES for table info, and USER_INDEXES or DBA_INDEXES for index info to name a few. Some of the data in these tables is populated by executing the ANALYZE command on the tables. These are a few of the many available. They are well covered in the Oracle documentation and on Oracle's MetaLink. Baan also details how it is implemented within Oracle in it's Oracle driver documentation.
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