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Entry type: FAQ Entry ID: 109755846, Entry date: 01/31/2020

What are the system limits of the OPC UA Server with S7-1500 and S7-1200?

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The following tables give you the system limits of the OPC UA Server with S7-1500/S7-1200 CPUs, ET 200 CPUs, Software Controllers and Open Controllers.

1. System limits of OPC UA server for S7-1500 CPUs

Table 1 shows the system limits of the OPC UA Server with S7-1500 with firmware V2.8.x:

Property CPU
1510, 1511, 1512, 1513 1515, 1516, 1505S 1517, 1518, 1507S 
Maximum number of subscriptions with more than 1000 monitored elements per subscription over all sessions1010


Maximum number of subscriptions with a maximum of 1000 monitored elements per subscription over all sessions

Maximum number of subscriptions per session202020
Smallest possible sampling interval100 ms100 ms10 ms
Smallest possible Send interval500 ms200 ms10 ms
Maximum number of sessions324864

Table 1


  • The number of 10,000 elements per subscription is always the maximum.
  • A subscription with a maximum of 1000 elements cannot be converted into a subscription with more than 1000 elements.
  • With regard to performance, it does not matter over how many subscriptions the elements to be monitored are distributed.
    • Variant A: Large number of subscriptions with small number of elements.
    • Variant B: Small number of subscriptions and large number of elements.
    • The difference is the larger main memory requirement in Variant A.
  • If you try to register more elements in a subscription than specified in the table above, the status code "BadTooManyMonitoredItems" is returned in the OPC UA client. In this case the client should attempt to register the remaining elements via another subscription.
  • If the maximum quantity framework of the OPC UA server is exceeded, the OPC UA server sends the status "BadOutOfMemory" to the OPC UA client.
  • Independent of the system limits mentioned above it is recommended not to exceed the number of elements to be monitored specified in Table 2 as overall quantity framework of the server.

Property CPU

1510, 1511, 1511C,

1513, 1505S 

1515, 1516  1517, 1518, 1507S 
* Recommended maximum number of monitored elements over all subscriptions10002000 10000

Table 2

* These recommendations are based on a user program with the following conditions:

  • Only OPC UA communication (no other communication, like TCP, for example, is executed).
  • Sampling and Send interval of 1 second.
  • No OBs with priority greater than 15 (this means no interruption of the communication through OB processing).
  • 50% maximum communication load

  • Data type of the elements: WSTRING 

2. System limits of OPC UA server for S7-1200 CPUs

Adjacent table shows the system limits of the OPC UA Server with S7-1200 with firmware V4.5:

Subscription limitationsMin. Max. 
​Minimal sampling interval100 ms, 250 ms, 500 ms, 1000 ms, 5000 ms, 10000 ms
Minimum publishing interval200 ms20.000.000 ms
Number of sessions 10
Number of subscriptions per session 50

Number of nodes for user-defined server interfaces

​Max monitored nodes100


3. Further Information

More information you will find in the TIA Portal information system, under:

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