Stored procedures have been available in DB2 z/OS since v5, but were limited in that they needed to be written in a third generation language such as COBOL or C, and implemented as an external stored procedure running in a Workload Manager (WLM) controlled address space.
The SQL Procedures Language has been available since v5, in which DB2 z/OS stored procedures could be written in a native DB2/SQL language that is a subset of the ANSI SQL/PSM language standard. But to implement an SQL Procedure prior to DB2 v9, the SQL/PL stored procedure needed to be precompiled and translated into a C program, which would then in turn be compiled and implemented as an external stored procedure.
Since Phoenix was not licensed for a C compiler on our mainframe environment, the use of SQL Procedures on DB2 z/OS was not an option prior to DB2 v9.
The native SQL Procedures support introduced in DB2 v9 removes this restriction. Stored procedures now written in SQL/PL no longer need to be precompiled and converted to C programs. They can now be run natively directly within the DB2 engine.