Compilation of a package

Compilation of the package in PL/SQL is the process of transforming the specification of the package and body of the package into the format which is Oracle database can be efficiently executed. This process verifies the syntax and the semantics of the PL/SQL code and resolves any references to the objects of other databases and it will generate the necessary executable code. Now we can discuss the steps which are involved in the package compilation.

• Parsing: The first step of compiling a package in PL/SQL is parsing. Parsing is nothing but, it is dividing the code into individual components like identifiers, keywords, and operators. It will check the syntax and the rules of the PL/SQL. In this step, you can know the syntax errors in the code like incorrect keywords and missing semicolons etc.
• Semantic Analysis: After completion of the parsing, the compiler will perform the semantic analysis on the code. Semantic analysis is nothing but, it checks the code for semantic errors like referencing the undefined variables or using the incorrect data types. It also checks the code that follows the rules and regulations of the PL/SQL language. If any semantic errors are found in the code, the compilation will fail and it will generate the error message.
• Dependency Resolution: The compiler will check the dependencies between the package which is ready to be compiled and objects of the other database. It involves checking the references to the tables, views, functions, procedures, types, or other packages. If any one of the referenced objects does not exist or is invalid in the code, the compilation will fail.
• Compilation of Package Specification: After the completion of the above processes such as parsing, semantic analysis, and dependency resolution, the package specification is successfully compiled. The compiler will verify the declarations of the public procedures, functions, types, variables, and exceptions which are specified in the package specification. It will generate an execution plan for every public function and procedure. After these steps, the database will execute the code efficiently.
• Compilation of Package Body: After the completion of the package specification compilation, the compiler will be ready to compile the body of the package. The compiler will generate the executable code for every procedure and function in the body of the package, and make sure that the implementation of the package body matches the declarations in the specification of the package.
• Error Handling: While compilation, if any errors occur like compilation errors, semantic errors, syntax errors, or unresolved references, the compilation will fail and display the error message on the screen. The error message contains the nature of the error and placed in the code, it will help the developers for identifying the issues and resolve them issues.
• Code Generation: After the completion of compilation, the compiler will generate the compiler code for the package. This code will be optimized for the execution by the database of the Oracle and make the package ready to use.
• Status Update: Finally, after completion of all the above steps, the status of the package is updated in the dictionary of the database. It indicates that the code has successfully compiled and is available for usage by other PL/SQL code.

PL/SQL ( Procedural Language/Structural Query Language ) is the extension of SQL ( Structured Query Language ) which is allowed to the developers for creating the procedural logic along with the Oracle database. The package is one of the main key componentss of PL/SQL development.

The PL/SQL package is the group of the related procedures, functions, variables, and other bundled constructs for providing the modularity and organized approach to application development. In PL/SQL, the package specification gives the blueprint of the functionalities that are provided by the PL/SQL package.

It is defined by the interface along with the PL/SQL code which interacts with the package. It works like an API ( Application Program Interface ) that defines how the external programs can interact with the software library.