Search notes:

Oracle: DBA_OBJECT_SIZE

Sizes, in bytes, of various PL/SQL objects.

This view is created in prvtpool.plb, possibly in relation with dbms_shared_pool.

select
  owner,
  name,
  type,
  source_size,
  parsed_size,
  code_size,
  error_size
from
  dba_object_size
order by
  owner,
  greatest(source_size, parsed_size, code_size) desc;

Github repository Oracle-Patterns, path: /Installed/data-dictionary/object/size/show.sql

The column parsed_size returns the number of bytes of the «flattened» DIANA.

However, it's not possible to estimate the number of DIANA nodes from this value.

See also the PL/SQL error PLS-00123: program too large.