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OPC-Server Data Sheet

Created by Werner Krings, Tani GmbH
Date: 2019.7.1

Technical Data Opc Server


The Tani OPC Server is a multi protocol and multi OPC server. It allows access to coltrollers and devives from various manufactuters. It is easily to configure. It offers a lot of diagnostics functions.

OPC Interfaces

The maximum number of OPC clients is depending on used resources only. A PC from 2014 can handle multiple hundred connections.
All OPC interfaces are working locally in one PC or over network.
in case of Classic OPC Classic please do not use DCOM over networks, but it will be supported.
OPC UA supports the fast binary protocol. Security is supported in all variants. Multicast discovery is supported.
Data access data items are supported up to 200K each.

OPC UA functionality and limitations

The OPC UA implementation conforms to the specification 1.04.
An internal discovery server is active on standard, it supports multicast discovery also. It can be used as a global discovery server. Alternatively an external discovery server can be configured.

The session timeout will be limited to one hour.
AddNodes is supported with the following restrictions:

Traffic between different OPC interfaces (tunneling) is supported. It will be used for the OPC DA tunnels.

Controller Interfaces

All controllers will be connected over network. Often this is Ethernet, WLAN or other networks. All serial Ethernet and MPI Ethernet gateways for industrial controllers usage are supported.

Configuration Interfaces

The configuration can be done with the shipped configuration software or over OPC with the System topic.
The connection  for the configuration is encrypted with TLS 1.2. The encryption can be switched off for usage in countries where encryption is forbidden.

Network Redundancy for connections to controllers and devices

Connections to devices and controllers are supporting network redundancy.
Double and triple redundancy can be selected.
Two redundancy operation modi are possible.
In dynamic redundancy any of the connections is working as master. If it breaks another connection becomes the master connection.
In static redundancy the first connection is the master. If it breaks another connection becomes the master. If the first connection works again it will become the master connection again.

The connections of the redundancy should work on different netaork adapters.The adapters need different IP subnets for proberly work..

Controller Types and Controller Protocols

Communicates via Ethernet.


BACnet will be used over IP / UDP.
Maximum length of strings: 256 Byte
Status text elements are supported (state_text)
Supported charsets: UTF-8, UTF-16, Latin-1
Unions ("Choice") and structures ("Sequence") are existing for important values. All unimplemented instances will not be shown.
Enum values are represented as UINT32. Some special enum are handled as bool.
Values in "Octet-String" and "Bit-String" can be written in whole only.

BBMD (BACnet Broadcast Management Device) details

BBMD will be used during the connection establishing and the device search if the devices do not be all in the same collision domain. BACnet uses broadcast during ist connection establishing.
There are several procedures in BBMD:

Additionally BBMD can be used connecting older serial only installations to the IP network.

COV (Change Of Values) details

COV represents the event subsystem of BACnet. Events will be offered in browsing the variables, they will be subscribed. If the device will send the data the event will be generated.
Because BACnet is working with UDP the COV receive can not be guaranteed. Tani is offering an option: If no event will be received during the reconnection time from the configured connection it will be polled. If the value did not change no event is send for this polling.

BACnet - Writing values with priority-array

These object types have a priority-array in addition to their present-value property: The BACnet spec says: The Tani implementation works as follows:

This mechanism was chosen to allow choosing the write priority via OPC without changing the read syntax for present-value property. This also allows writing NULL values via OPC.

Logger for diagnostics

The OPC Server contains a logger for diagnostics purposes during plant startup. The logger can be configured. The system load can be big if all controller data in big plants are logged.


Maximum number of configurable client connections: 4000.
Maximum length of a single item: 4GB.
Maximum number of elements each connection: 1 million.
Maximum number of elements (Items): 16 million.
Maximum OPC groups each connection: 100.
Maximum number of passive connection for each port is 999.
The OPC synchronous functions returning a bad quality immediately if the PLC connection is not established.
Changes in controller configuration will be checked all 10 seconds if the PLC does not offer a mechanism for this check during write.
Fields can be up to 64K in length each.
Multi dimensional arrays can have up to six dimensions.

Simulation of plc connections

Connections and their data can be simulated.
Read data creates the elements with value zero. Write will change the content. The changed values will be returned as new data.

Depending on the license the limits can be less.


The throughput will be mainly limited by the controller speed or the reaction time of OPC applications.
Read requests to the controller will be optimized as much the controller is supporting this. For that elements will be collected to blocks reading more than requested, but not for inputs and outputs. These optimizing can be affected by configuration separately for each connection. Optimizing can be switched off, too.
Write requests to the controller are collected or handled in that order the application did called the system.
On OPC all optimizing the individual OPC uses is supported.
The normal time in cyclic controller requests is 50ms.It can be faster if the controller polling interval is set to zero.
Only data are sent to OPC which did change in the controller between two read requests.

Field and text optimizings

The from version 1.8 existing field optimizings will prevent reading the long fields too often, the index is requested on standard only.This optimizing bases of the fact that the index does net changed too frequently.

Usage of memory

Usage of computation time

The consumed computation time is depending on the load with communication. Most the time it will be waited for controller data or OPC application reaction.
All software is working with events. This maximizes the throughput and minimizes the usage of computation time.
Multiple CPU are supported. Up to ten CPU will be used, the main work will be handled by three CPU.


The installation does depending on the product install multiple parts separately. On uninstall not all products are deleted automatically. But all installed products can be deleted over the menu or the software part in the system control manager.
The user settings will be preserved and not deleted during uninstall.

Operating systems