What is a package of procedures? What does it consist of?

A package of procedures is a logical group of related procedures and functions in a database, combined under a single name. It serves to organize and encapsulate code, enhancing its reusability and manageability.

Main components of a procedure package:

• Specification — declaration of all procedures, functions, data types, and variables available externally. This is the package interface.
• Body — implementation of all procedures and functions declared in the specification. The logic is described here.

Packages allow:

• To hide internal implementation (encapsulation).
• To declare global variables and constants.
• To improve performance through compilation and caching.

Example (Oracle PL/SQL):

CREATE OR REPLACE PACKAGE my_package AS
  PROCEDURE proc1(param IN NUMBER);
  FUNCTION func1 RETURN VARCHAR2;
END my_package;
/

CREATE OR REPLACE PACKAGE BODY my_package AS
  PROCEDURE proc1(param IN NUMBER) IS
  BEGIN
    -- implementation
  END proc1;

  FUNCTION func1 RETURN VARCHAR2 IS
  BEGIN
    RETURN 'result';
  END func1;
END my_package;
/