Data integrity

VLF constitutes a form of “shared” storage in that data placed into VLF as a result of one user's processing might later be returned to many other users. Given this fact, it is obvious that your application must include controls to protect the integrity of the data to be stored in VLF.

The VLF environment provides some of the required integrity. All VLF macros, with the exception of the object retrieval (COFRETRI) macro, require that the caller be running in supervisor state or with PSW key mask 0-7. Thus, VLF can guarantee that, once an object is created in VLF storage, it cannot be modified by unauthorized code. VLF cannot, however, guarantee that the data stored in VLF in the first place is correct; your application must ensure the integrity of the data to be stored in VLF.

The best way to provide this integrity is to design your application so that objects are created by authorized code using system key storage. See Creating a VLF object for details.