1. Overview of PCS 7 AS Runtime License and Process Objects
SIMATIC PCS 7 enforces a runtime-license model on every Automation Station (AS). Each license is sized in Process Objects (PO). A PO is the licensing unit that PCS 7 uses to meter the executable workload of an AS program: every CFC chart, every SFC instance, every block instance that the AS runtime engine touches is normalized into a PO count and compared against the installed AS runtime license key. The license key itself is held on a USB stick or transferred into the AS hardware's license container.
The standard count unit is sold in batches of 100 POs. The catalog number for a single PO 100 runtime license is:
- 6ES7658-2XA00-0XB0 – SIMATIC PCS 7 Runtime License OS (PO 100), single license for 1 installation, License Key on USB stick, without software and documentation. See the official Siemens product entry at PCS 7 Runtime License OS (PO 100) product page.
Each AS download decrements PO slots from the available count. If a project expands past the licensed quantity, the AS enters a license-violation state and operator control degrades (alarm-acknowledgement restriction, OS lockout, or refusal to download new charts). License administration is therefore a runtime safety task, not a procurement detail.
2. Process Object Definition and Counting Rules
A Process Object is not a CFC block; it is a billing unit derived from chart topology. PCS 7 evaluates every CFC/SFC under the S7 program and maps them to a deterministic PO value. The official mapping rules are documented in the SIMATIC Manager help under "Count and Booking of the PO License".
Where the counting rules live
-
PCS 7 V7.1: Open any CFC chart in SIMATIC Manager, press
F1, search the index for book or booked, and select the topic Count and Booking of the PO License. -
PCS 7 V7.0: Switch to the Component View, expand the S7 program to the chart folder, right-click, hover over Charts → BookBack Process Object without clicking, and press
F1to display the topic.
What counts as one PO (typical mapping)
| Project Element | PO Charge | Notes |
|---|---|---|
| CFC chart with one driver block (e.g. CTRL_PID, MOT_SPEED) | 1 PO | Base charge per chart with standard I/O driver |
| Additional driver/function block in same chart | 0.5 PO each (rounded) | PCS 7 normalises sub-blocks per published table |
| SFC instance with operator dialog | 1 PO | Sequential function chart with OS faceplate |
| SFC instance without operator dialog | 0.5 PO | Internal step chain only |
| User-defined FBs called from a chart | Counted as part of parent chart | Does not multiply PO; see section 7 |
| WinCC OS picture objects (alarms, tags, screens) | Separate OS license | Does not affect AS PO; see section 7 |
3. AS Runtime License Deduction Behavior
PCS 7 does not consume a license on every download. It applies a delta model.
3.1 First download (cold start of a licensed AS)
- SIMATIC Manager enumerates every CFC, SFC, and runtime block under the target S7 program.
- The tool computes the total PO demand of the project.
- The computed value is subtracted from the installed AS runtime license on the AS (license key held in the CPU or in the SIMATIC Automation License Manager).
- The remaining license slots are written to the AS for runtime enforcement.
Example: A project contains 150 POs and the license key holds 250 POs. After the first download, the AS reports 100 free PO slots (250 − 150 = 100).
3.2 Subsequent downloads (delta model)
- SIMATIC Manager reads back the current PO allocation from the AS.
- It compares the new project PO count with the previously booked PO count.
- If the new count is higher, only the delta is subtracted from the remaining license pool.
- If the new count is equal or lower, no additional license is deducted and previously booked POs are released back to the pool.
This delta behavior is why license enforcement remains stable across iterative engineering: adding charts consumes new license; deleting or re-using charts frees license automatically on the next download.
4. Prerequisites for License Management
Before any bookback or recovery operation, verify the following on the Engineering Station (ES):
- SIMATIC Manager installed at the same major version as the AS firmware target (V7.x, V8.x, or V9.x).
- Automation License Manager (ALM) installed and able to communicate with the USB license stick or the central license server.
- The S7 project file on the ES is the same revision that was last downloaded to the AS. PCS 7 will only book back license for the project that matches the AS state.
- Online connection to the AS via MPI/Profibus/Ethernet (whichever the project was compiled against) is required for any bookback action.
- User account with the SIMATIC Logon role assigned to the project (typically Engineer or Project Editor).
5. Bookback License Procedure
Bookback is the operation that returns PO license slots from a live AS back to the Engineering Station's available pool. Use it before any of the destructive events listed in section 6.
5.1 Bookback to the same AS (preview and confirm)
- In SIMATIC Manager, open the S7 project in Component View.
- Select the chart folder of the target AS.
- Right-click and choose Charts → BookBack Process Object.
- The dialog displays the current PO allocation of the AS and the PO demand of the open project. If the values do not match, PCS 7 will refuse the bookback because the project is no longer the source-of-truth of the running AS.
- Confirm the bookback. SIMATIC Manager writes the freed PO slots back to the license key on the ES.
5.2 Bookback when the AS is unreachable
- Open the project on the ES that was last downloaded to the AS.
- Navigate to Charts → BookBack Process Object in the chart folder.
- If the AS is offline, PCS 7 will prompt to perform an offline bookback. The PO count that was last downloaded is removed from the AS license key (held in the local license container) and returned to the ES pool.
- Document the bookback ticket number returned by SIMATIC Manager. Siemens support can use this ticket if license recovery is disputed.
6. Recovery Scenarios After AS Hardware Loss
PCS 7 ties PO license to the pair of CPU and memory card, not to either device alone. The pairing logic drives the recovery strategy.
6.1 Scenario A – CPU replaced, memory card retained
Insert the original memory card into the new CPU. On the next online connection from SIMATIC Manager, the AS reports the PO count that was previously booked. The license survives because the project and PO allocation are stored on the card.
6.2 Scenario B – Memory card replaced, CPU retained
Insert a new card and download the same project from the ES. PCS 7 sees a clean AS, but it recognises the prior PO count from the license container inside the CPU. The previously booked POs are automatically restored and the project downloads without re-deducting license.
6.3 Scenario C – Both CPU and memory card lost
This is the only configuration in which the PO license is genuinely lost. PCS 7 cannot prove what was booked, so it does not restore license. To proceed:
- Replace both CPU and memory card with equivalent hardware.
- Perform a full project download from the ES.
- PO license equal to the project size is deducted from the license pool. If the pool cannot cover the demand, the download completes but the AS enters license-violation mode.
- Contact Siemens support with the project ID and PO count to request a manual license replacement only if you have proof of the original purchase and the lost device serial numbers.
6.4 Scenario D – CPU memory reset (MRES)
MRES clears the work memory and the runtime license container. The flash memory card retains the project and the PO allocation. The next online connection from SIMATIC Manager restores the PO count automatically, identical to scenario B.
6.5 Decision flow
7. AS Runtime PO vs WinCC OS PO
PCS 7 enforces two independent license pools: one on the AS (S7 runtime) and one on the OS (WinCC runtime). They do not share counters and are procured separately.
| Aspect | AS Runtime PO | WinCC OS PO |
|---|---|---|
| Enforced on | AS CPU (S7-400 / S7-410) | OS server / OS client (WinCC) |
| Catalog | 6ES7658-2XA00-0XB0 (PO 100) | 6ES7658-2... (OS PO bundles, separate MLFB) |
| Counted objects | CFC charts, SFC instances, runtime blocks | Tags, alarms, picture objects, archive tags, user archives |
| Counted by | SIMATIC Manager at AS download | WinCC Explorer / OS Project Editor at OS compile |
| User-defined FBs | Counted as part of parent chart (no extra PO) | Tags mapped to the FB inputs are still counted as OS tags |
| Typical sizing trigger | Plant expansion adds new CFCs/SFCs | New faceplates, new alarm classes, new picture objects |
8. PO 100 License Specifications
| Attribute | Value |
|---|---|
| Catalog number (MLFB) | 6ES7658-2XA00-0XB0 |
| Product name | SIMATIC PCS 7 Runtime License OS (PO 100) |
| License scope | Single license for 1 installation |
| Delivery form | R-SW (Runtime Software), License Key on USB stick, no software, no documentation |
| Increment | 100 Process Objects |
| Target system | PCS 7 AS / OS runtime |
| Required tool | Automation License Manager |
For larger plants, multiple PO 100 licenses are stacked. The Automation License Manager aggregates the keys into a single pool. A typical mid-size plant uses 3–6 stacked PO 100 licenses (300–600 PO).
9. Verification Steps After a License Operation
- Open SIMATIC Manager and the S7 project on the ES.
- Navigate to Charts → Process Object in the chart folder. Record the displayed PO demand.
- Open Automation License Manager on the ES and inspect the license key. Confirm the residual PO count = installed PO − booked PO.
- Go online to the AS. In the CFC/SFC editor, select Charts → PO Booked (or the equivalent dialog in your PCS 7 version). Confirm the AS reports the same booked PO value as the ES.
- If values disagree, perform a bookback from the AS side and re-issue the download to resynchronise.
10. Troubleshooting Matrix
| Symptom | Likely Cause | Corrective Action |
|---|---|---|
| Download completes but AS enters license-violation mode | Project PO demand exceeds installed PO | Size license with additional PO 100 bundles (6ES7658-2XA00-0XB0); perform bookback of unused AS slots first |
| Bookback reports “project does not match AS” | ES project was modified after last download | Restore the last-downloaded project revision from archive, or download current project then bookback |
| PO count lost after CPU replacement | Memory card was also replaced or not transferred | Re-insert original memory card; PO allocation is stored on the card |
| PO count lost after card replacement | CPU license container was also reset | Insert original CPU; license container holds PO allocation |
| License counter in ALM shows negative residual | Multiple engineers downloading concurrently | Centralise downloads; reserve a single ES as license master |
| OS compile error “RPC server is unavailable” (V8.2) | OS project editor cannot reach AS during compile | Verify network path to AS, re-import AS, retry OS compile |
| Bookback button greyed out | User lacks SIMATIC Logon role for bookback | Assign Engineer / Project Editor role in SIMATIC Logon |
11. Field-Proven Cautions
- Always bookback before any planned CPU firmware update that involves a memory card reformat. The reformat clears the project and the PO allocation synchronisation marker.
- Keep one PO buffer of at least 10% above the steady-state project demand. Live engineering will eat that buffer faster than procurement can close a PO order.
- Treat PO 100 license USB sticks as controlled media. They are not interchangeable with WinCC OS PO licenses even though the catalog family is similar.
- For PCS 7 V8.2 and later, the OS compile step that fires the “RPC server is unavailable” error is independent of the PO license path. Do not mistake it for a PO issue.
12. FAQ
Does every AS download subtract a full Process Object from my license?
No. The first download subtracts the full project PO count. Subsequent downloads use a delta model: PCS 7 reads back the current PO allocation, compares it to the new project demand, and only deducts the difference (or releases PO if the project shrank).
What happens to the AS runtime license if I perform an MRES on the CPU?
MRES clears the CPU work memory and license container, but the memory card retains the PO allocation. On the next online connection from SIMATIC Manager, the previously booked POs are restored automatically. License is not lost.
What is the catalog number for a single PCS 7 PO 100 license?
The catalog number is 6ES7658-2XA00-0XB0 – SIMATIC PCS 7 Runtime License OS (PO 100), single license, License Key on USB stick. See the official product page.
Can I lose PO license by replacing only the CPU or only the memory card?
No. License is tied to the pair of CPU and memory card. Replacing either device alone is recoverable. License is only lost when both devices are destroyed and you no longer have the project source-of-truth to prove the previous PO count.
Is the AS runtime PO the same as the WinCC OS PO?
No. They are two independent license pools. AS runtime PO meters CFC/SFC execution on the CPU. WinCC OS PO meters tags, alarms, and picture objects on the OS server. A project must satisfy both pools independently.
Where do I find the official PO counting rules in SIMATIC Manager?
In PCS 7 V7.1, open any CFC, press F1, search for book or booked, and open Count and Booking of the PO License. In PCS 7 V7.0, expand the chart folder in Component View, right-click, hover over Charts → BookBack Process Object, and press F1.
Do user-defined FBs add to the PO count?
User-defined FBs called from a CFC are counted as part of the parent chart, not as additional POs. The PO charge is determined by the chart topology, not by the number of contained block instances. Verify the exact rule in the SIMATIC Manager help for your PCS 7 version.