A stored procedures(PSM, Persistent Stored Modules) of ALTIBASE HDB might be divided into three as below.

What's Stored Procedure

Stored procedure is very similar tool to the ORACLE's PL/SQL in concept. 

Stored procedure is one of database object comprising SQL statement, Control flow statement, exception handler, etc. 

Stored procedure is created in advance, compiled, and stored in database, ready for execution.

In that state, Stored Procedure can be simultaneously accessed by multiple SQL statements.

The term “Stored Procedure” is sometimes used to refer to the Stored Procedure and Stored Function collectively.

The Stored Procedure and Stored Function differ only in that Stored Function returns a value to the calling application, whereas the Stored Procedure does not.

The ALTIBASE Stored Procedure's overall syntax is very similar to the ORACLE's PL/SQL statement. 

Basic syntax of the procedures used in ORACLE's PL/SQL is almost same with  ALTIBASE Stored Procedure,

So you can easily convert the ORACLE PL/SQL to the ALTIBASE Stored Procedure except for some functions which are not supported in the ALTIBASE HDB.

We call these ALTIBASE Stored Procedure to the ALTIBASE PSM ( Persistent Stored Modules) with a different name.

ALTIBASE Stored Procedure can be made with 'CREATE PROCEDURE' and 'CREATE FUNCTION' statement that has synax of ORACLE PL/SQL.

For further information about these statements, please refer to 'ALTIBASE Stored Procedure Manual'.(ALTIBASE Stored Procedure Manual)