1. A computer-implemented method of persisting machine instructions, the method comprising: storing into a database, software expressed in an intermediate level language (ILL); interpreting the ILL software in a virtual machine in a database management system; operating a compiler in the database management system, to receive the ILL software as input and to emit native code comprising said machine instructions; storing the native code emitted by the compiler in the database; storing in the database an indicator of a plurality of properties required to execute the native code; checking if said indicator stored in the database matches a new indicator of said plurality of properties; executing said machine instructions in the native code emitted by the compiler, via the virtual machine in the database management system, if a result of said checking is true; and marking the native code as invalid if said result of said checking is false.