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valz · Member 3 Joined: 26 Jul 2015 Posts: 771

What is the meaning of the WinCC message "No access to SQL Server, data loss possible."?
https://support.industry.siemens.com/cs/document/109813481/
The message "No access to SQL Server, data loss possible." appears if WinCC cannot write the values and messages into the SQL database.
This can occur in the following cases:
The affected OS server is overloaded.
There is a flood of messages (flood of messages in the Alarm Logging).
The affected OS server has not been allocated enough memory (RAM) for the SQL server.
An attempt has been made to archive invalid values in the WinCC database.
(For example, division by a value of '0' results in a NaN = Not a Number.)
If the power saving mode is activated in the power management for the network cards used.
Important
WinCC archives the values as BLOB data (Binary Large Object). This message occurs if the system cannot write this BLOB. However, WinCC immediately tries to save this data block until it is successful (until no message is displayed). This message appears only when an archiving process is unsuccessful and no BLOB data can be written to the database.
If the WinCC data is successfully archived by a properly functioning archiving process, no message is generated in order not to generate a message flood.

Possible remedies
It is recommended to configure 50% of the installed memory for SQL Server.
How can you optimize the processing of tasks in SQL Server in the PCS 7 environment?
https://support.industry.siemens.com/cs/document/109812306/
There are too many segments attached on the SQL Server, or the segment size is too large.
More information about how many individual segments can be connected to SQL Server in PCS 7 without performance limitations is available in the following entry:
How many single segments can be connected to the SQL server in PCS 7 without impairing performance?
Recommended settings:
https://support.industry.siemens.com/cs/document/34473263/
Weekly segments
Total time period for all segments of maximum 6 months
How do you optimize your backup and recovery strategy for the WinCC archive of your PCS 7 project?
https://support.industry.siemens.com/cs/document/109808141/
In addition, you can start an analysis to find the reason locally with the Windows System Monitor (System Monitor). See the following FAQ: How do you save the diagnostics data of the Windows system monitor (performance monitor) in a file?
https://support.industry.siemens.com/cs/document/23782899/

If the above optimizations do not solve the problem, a more in-depth analysis is required as part of Extended Support. Note that the following information is required to perform the analysis.

The collection of diagnostics data with the SAS DC (SIMATIC Assessment Suite - Data Collector) from the server concerned.
https://support.industry.siemens.com/cs/document/65976201/
A screenshot of the last appearance of this message from the process control list.
When was the last time this behavior occurred? (Date/time)
Is this behavior reproducible or sporadic?
Is there a scenario in which this problem occurs? (total load, delta load, specific screen selection, confirmation, failure of a module).
When does this effect occur or what exactly was changed before the behavior occurred the first time? (Update, RF installation, change of configuration,....)
Overview of the system configuration (network plan with number of servers, OS clients and Engineering Stations).
Are you running the system on the OS servers?
Screenshots of the segment settings of Tag Logging and Alarm Logging on the ES.
"Right-click the OS Server project in the SIMATIC Manager > Open Object" > Open the editors for TagLogging and AlarmLogging in the WinCC Explorer and make screenshots of the archive configuration.
A collection of the contents of your OS Server drives:
To do this, you open CMD and enter the following command, "dir /S "drive to be read" > "destination path of the text file"\"name".txt". This creates a text file with the contents of the drive.
Example:
"dir /S C:\ > C:\info_drive_C.txt" saves the content of drive C in the text file "info_drive_C.txt" directly on drive C.