The Oracle Database Gateway for Teradata User's Guide translates a query that refers to an Oracle database data dictionary table into a query that retrieves the data from Teradata system catalog tables. You perform queries on data dictionary tables over the database link in the same way you query data dictionary tables in the Oracle database. The gateway data dictionary is similar to the Oracle database data dictionary in appearance and use.
This appendix contains the following sections:
The following paragraphs describe the Oracle Database Gateway for Teradata data dictionary support.
Teradata data dictionary information is stored in the Teradata database as Teradata system catalog tables. The Teradata system catalog tables define the structure of a database. When you change data definitions, Teradata reads and modifies the Teradata system catalog tables to add information about the user tables.
Accessing a gateway data dictionary table or view is identical to accessing a data dictionary in an Oracle database. You issue a SQL SELECT
statement specifying a database link. The Oracle database data dictionary view and column names are used to access the gateway data dictionary in an Oracle database. Synonyms of supported views are also acceptable. For example, the following statement queries the data dictionary table ALL_CATALOG
to retrieve all table names in the Teradata database:
SQL> SELECT * FROM ALL_CATALOG@TERA;
When a data dictionary access query is issued, the gateway:
Maps the requested table, view, or synonym to one or more Teradata system table names. The gateway translates all data dictionary column names to their corresponding Teradata database column names within the query. Refer to "Data Dictionary Mapping" for details.
Sends the translated query to Teradata.
Might convert the retrieved Teradata data to give it the appearance of the Oracle database data dictionary table.
Passes the data dictionary information from the translated Teradata system catalog table to the Oracle database.
Note:
The values returned when querying the gateway data dictionary might not be the same as the ones returned by the Oracle Enterprise ManagerDESCRIBE
command.Queries issued directly to individual Teradata system catalog tables are allowed but they return different results because the Teradata system catalog table column names differ from those of the data dictionary view. Also, certain columns in a Teradata system catalog table cannot be used in data dictionary processing.
The gateway supports the following views and tables:
Supported Views and Tables | Supported 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 |
DBA_CATALOG |
DBA_COL_COMMENTS |
DBA_OBJECTS |
DBA_TABLES |
DBA_TAB_COLUMNS |
DBA_TAB_COMMENTS |
DICT_COLUMNS |
DICTIONARY |
DUAL |
USER_COL_COMMENTS |
USER_CATALOG |
USER_CONSTRAINTS |
USER_CONS_COLUMNS |
USER_INDEXES |
USER_IND_COLUMNS |
USER_TAB_COLUMNS |
USER_OBJECTS |
USER_TABLES |
USER_TAB_COMMENTS |
USER_VIEWS |
USER_USERS |
No other Oracle database data dictionary tables or views are supported. If you use a view not on the list, you receive the Oracle database error code for no more rows available.
Queries through the gateway of any data dictionary table or view beginning with ALL_ can returns rows from the Teradata database even when access privileges for those Teradata objects have not been granted. When querying an Oracle database with the Oracle data dictionary, rows are returned only for those objects you are permitted to access.
The tables in this section list Oracle data dictionary view names and the equivalent Teradata system tables used. A plus sign (+) indicates that a join operation is involved.
Table C-1 Oracle Data Dictionary View Names and Teradata Equivalents
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There is a minor difference between the gateway data dictionary and a typical Oracle database data dictionary. The Oracle database columns that are missing in a Teradata system catalog table are filled with zeros, spaces, null values, not-applicable values (N.A.), or default values, depending on the column type.
The gateway data dictionary tables and views provide the following information:
Name, data type, and width of each column
The contents of columns with fixed values
They are described here with information retrieved by an SQL*PLUS DESCRIBE
command. The values in the Null? column might differ from the Oracle database data dictionary tables and views. Any hardcoded default value is shown to the right of an item, but this is not information returned by DESCRIBE
.
Name | Type | Value |
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