LN data dictionary

A data dictionary is a catalog that provides information about the data in a database. You can think of a data dictionary as “data about data,” or metadata. You can use a data dictionary to find data that resides in a database table.

The LN database drivers maintain a data dictionary because the data that LN applications use can differ from the database tables defined in the RDBMS. The LN data dictionary maps LN data types, domains, schemas, and referential integrity information to the appropriate information in the RDBMS. To store or retrieve data in the RDBMS, the database driver maps data dictionary information to database table definitions.

LN data dictionary information can be stored in shared memory, where the information will be available to all running LN application virtual machines. The data dictionary information is shared among all the open sessions in a single database driver.

The database driver cannot directly use the LN data to create Oracle tables because not all LN data types exactly match Oracle data types. To create valid Oracle tables, the driver must perform some mapping or translation. To map the LN data dictionary with tables in Oracle, conventions are used for the table names, column names, and index names.