Explain declaring shared constants, types and cursors in a package specification

Anything declared in the spec is public: reference it as pkg.name. Put status codes and magic numbers there as CONSTANT, shared collection/record TYPEs so callers can declare variables of pkg.type_name, and public cursor declarations (spec has the header, body has the SELECT). This gives one authoritative definition and lets client code compile against the contract without seeing the body.

CREATE OR REPLACE PACKAGE invoice_pkg IS
  c_status_draw   CONSTANT VARCHAR2(1) := 'D';
  c_status_posted CONSTANT VARCHAR2(1) := 'P';

  TYPE invoice_id_tab IS TABLE OF NUMBER INDEX BY PLS_INTEGER;

  CURSOR c_unposted RETURN ap_invoices_all%ROWTYPE;  -- header only

  PROCEDURE post(p_ids invoice_id_tab);
END invoice_pkg;
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