The SPH3000 series has 'high-speed program (high-speed PG) memory' area in the program memory.
When you store a POU in this area, the POU execution speed becomes approximately three times faster.
The warning message means that the high-speed program memory space is low.
F.Y.I
If there is not enough high-speed PG memory to assign a POU, for example, by adding a circuit to the POU, the POU is assigned to the normal area.
Preferentially assign POUs that need to be processed at a high-speed to the high-speed PG memory, which is fixed to 224K bytes. Execute also the optimized compilation (compression of the execution codes) of the POUs assigned to the high-speed PG area, and re-assign the POUs of a low-priority task to the normal area.
* For more information on the specifications and usage of the high-speed PG memory, refer to the user’s manual 'SX-Programmer Expert (D300win) Reference (FEH257) version 'q' or later, '10-5 Optimized Compilation of POU (For SPH3000 series).'