What oracle data dictionary view can be used to decribe types defined in a plsql package

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Oracle

• Storage can hold multiple databases
• Databases can be opened by multiple instances
• Server can run run multiple instances
• A server can only run a single instace for any given database
• Data is stored in tablespaces
• A tablespace may be made up of multiple data files
• Tables/indexes/Materialized Views can be partitioned across multiple segments
• A segment lives on a tablespace
• A database object (table, index, stored program unit...) is owned by a user
• A table may be be referenced (through a foreign key constraint) by another table, including a table owned by another user
• A table may have at most one primary key constraint
• A table may have zero or more unique constraints
• A primary key or unique constraint is logically enforced by exactly one index (though you could have a multi-column unique constraint which is backed up by multiple unique indexes with the columns in a differing order)
• An index may be unique or non-unique. A unique constraint may be enforced by a unique or non-unique index.
• A table must have at least one column
• Each column has a datatype (and optionally a length or precision/scale)
• A trigger may relate to at most a single table. (Some triggers, such as SERVERERROR, don't relate to a table).

The column USER_TAB_COLS.virtual_column = 'YES' indicates if it's a virtual column.

You can get the expressions for each column with:

SELECT * 
FROM user_tab_columns
WHERE data_default IS NOT NULL;