Optimized or non-optimized  Block access

In TIA Portal, Data Blocks (DBs) can be created as optimized or non-optimized access. The difference mainly affects how the compiler organizes data and how you access it in your program.

Here’s a clear breakdown:

Non-Optimized DB (Classic / Standard DB)

• Memory layout is fixed and absolute ? every variable has a specific byte/bit address (e.g., DB1.DBX0.0, DB1.DBW2, etc.).
• Compatible with classic STEP 7 (Simatic Manager) style programming.
• Useful when:
• You need to access data via absolute addressing (e.g., from HMI, other PLCs, or older code).
• You want backward compatibility with older Siemens systems.
• Less efficient because:
• Data is stored with gaps and not packed efficiently.
• Bigger DB size due to fixed memory mapping.
• Slower access time compared to optimized.

Optimized DB

• Memory layout is dynamic and optimized by the compiler ? addresses are no longer fixed, but accessed symbolically (by variable name, not by absolute address).
• Improves:
• Memory efficiency ? compiler aligns and packs data efficiently.
• Execution speed ? faster read/write access.
• Variables are only accessible by symbolic names, not absolute addresses (e.g., MyDB.MyVar instead of DB1.DBW2).
• Best practice in new projects, unless absolute addressing is required.

Comparison Table

Rule of Thumb

• Use optimized DBs for all new projects (best performance, cleaner code).
• Use non-optimized DBs only if:
• You must interface with older STEP 7 projects.
• HMI/SCADA or external systems require absolute addressing.