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Data Dictionary Translation for Generic Connectivity

Generic connectivity agents translate a query that refers to an Oracle8i data dictionary table into a query that retrieves the data from a non-Oracle data dictionary. You perform queries on data dictionary tables over the database link in the same way you query data dictionary tables in Oracle8i. The generic connectivity data dictionary is similar to the Oracle8i data dictionary in appearance and use. Non-Oracle data dictionary information is supplied to the user in Oracle8i data dictionary format.

To better understand the data dictionary support provided by generic connectivity, read these sections:

• Data Dictionary Translation Support

• Data Dictionary Mapping

• Generic Connectivity Data Dictionary Descriptions

Data Dictionary Translation Support

Data dictionary information is stored in the non-Oracle system as system tables and accessed through ODBC or OLE DB application programming interfaces (APIs). This section contains the following topics:

• Accessing the Non-Oracle Data Dictionary

• Supported Views and Tables

Accessing the Non-Oracle Data Dictionary

Accessing a non-Oracle data dictionary table or view is identical to accessing a data dictionary in an Oracle database. You issue a SELECT statement specifying a database link. The Oracle8i data dictionary view and column names are used to access the non-Oracle data dictionary. Synonyms of supported views are also acceptable.

For example, the following statement queries the data dictionary table ALL_USERS to retrieve all users in the non-Oracle system:

SQL> SELECT * FROM all_users@sid1;
 

When you issue a data dictionary access query, the ODBC or OLE DB agent:

1. Maps the requested table, view, or synonym to one or more ODBC or OLE DB APIs (see "Data Dictionary Mapping"). The agent translates all data dictionary column names to their corresponding non-Oracle column names within the query.

2. Sends the sequence of APIs to the non-Oracle system.

3. Possibly converts the retrieved non-Oracle data to give it the appearance of the Oracle8i data dictionary table.

4. Passes the data dictionary information from the non-Oracle system table to the Oracle8i.

   Note: The values returned when querying the generic connectivity data dictionary may not be the same as the ones returned by the Oracle Enterprise Manager DESCRIBE command.

Supported Views and Tables

Generic connectivity supports only these views and tables:

• ALL_CATALOG

• ALL_COL_COMMENTS

• ALL_CONS_COLUMNS

• ALL_CONSTRAINTS

• ALL_IND_COLUMNS

• ALL_INDEXES

• ALL_OBJECTS

• ALL_TAB_COLUMNS

• ALL_TAB_COMMENTS

• ALL_TABLES

• ALL_USERS

• ALL_VIEWS

• DICTIONARY

• USER_CATALOG

• USER_COL_COMMENTS

• USER_CONS_COLUMNS

• USER_CONSTRAINTS

• USER_IND_COLUMNS

• USER_INDEXES

• USER_OBJECTS

• USER_TAB_COLUMNS

• USER_TAB_COMMENTS

• USER_TABLES

• USER_USERS

• USER_VIEWS

If you use an unsupported view, then you receive the Oracle8i message for no rows selected.

If you want to query data dictionary views using SELECT ... FROM DBA_*, first connect as Oracle user SYSTEM or SYS. Otherwise, you receive the following error message:

ORA-28506: Parse error in data dictionary translation for %s stored in %s

Using generic connectivity, queries of the supported data dictionary tables and views beginning with the characters "ALL_" may return rows from the non-Oracle system when you do not have access privileges for those non-Oracle objects. When querying an Oracle database with the Oracle data dictionary, rows are returned only for those objects you are permitted to access.

Data Dictionary Mapping

The tables in this section list Oracle data dictionary view names and the equivalent ODBC or OLE DB APIs used.

Table 9-1 Generic Connectivity Data Dictionary Mapping

View	ODBC API	OLE DB API
ALL_CATALOG	SQLTables	DBSCHEMA_CATALOGS
ALL_COL_COMMENTS	SQLColumns	DBSCHEMA_COLUMNS
ALL_CONS_COLUMNS	SQLPrimaryKeys, SQLForeignKeys	DBSCHEMA_PRIMARY_KEYS, DBSCHEMA_FOREIGN_KEYS
ALL_CONSTRAINTS	SQLPrimaryKeys, SQLForeignKeys	DBSCHEMA_PRIMARY_KEYS, DBSCHEMA_FOREIGN_KEYS
ALL_IND_COLUMNS	SQLStatistics	DBSCHEMA_STATISTICS
ALL_INDEXES	SQLStatistics	DBSCHEMA_STATISTICS
ALL_OBJECTS	SQLTables, SQLProcedures, SQLStatistics	DBSCHEMA_TABLES, DBSCHEMA_PROCEDURES, DBSCHEMA_STATISTICS
ALL_TAB_COLUMNS	SQLColumns	DBSCHEMA_COLUMNS
ALL_TAB_COMMENTS	SQLTables	DBSCHEMA_TABLES
ALL_TABLES	SQLStatistics	DBSCHEMA_STATISTICS
ALL_USERS	SQLTables	DBSCHEMA_TABLES
ALL_VIEWS	SQLTables	DBSCHEMA_TABLES
DICTIONARY	SQLTables	DBSCHEMA_TABLES
USER_CATALOG	SQLTables	DBSCHEMA_TABLES
USER_COL_COMMENTS	SQLColumns	DBSCHEMA_COLUMNS
USER_CONS_COLUMNS	SQLPrimaryKeys, SQLForeignKeys	DBSCHEMA_PRIMARY_KEYS, DBSCHEMA_FOREIGN_KEYS
USER_CONSTRAINTS	SQLPrimaryKeys, SQLForeignKeys	DBSCHEMA_PRIMARY_KEYS, DBSCHEMA_FOREIGN_KEYS
USER_IND_COLUMNS	SQLStatistics	DBSCHEMA_STATISTICS
USER_INDEXES	SQLStatistics	DBSCHEMA_STATISTICS
USER_OBJECTS	SQLTables, SQLProcedures, SQLStatistics	DBSCHEMA_TABLES, DBSCHEMA_PROCEDURES, DBSCHEMA_STATISTICS
USER_TAB_COLUMNS	SQLColumns	DBSCHEMA_COLUMNS
USER_TAB_COMMENTS	SQLTables	DBSCHEMA_TABLES
USER_TABLES	SQLStatistics	DBSCHEMA_STATISTICS
USER_USERS	SQLTables	DBSCHEMA_TABLES
USER_VIEWS	SQLTables	DBSCHEMA_TABLES

Default Column Values

The generic connectivity data dictionary differs from a typical Oracle database server data dictionary. The Oracle database server columns that are missing in a non-Oracle data dictionary table are filled with the following, depending on the column type:

• Zeros

• Spaces

• NULL values

• Default values

Generic Connectivity Data Dictionary Descriptions

The generic connectivity data dictionary tables and views provide this information:

• Name, data type, and width of each column

• The contents of columns with fixed values

In the descriptions that follow, the values in the Null? column may differ from the Oracle8i data dictionary tables and views. Any default value is shown to the right of an item.