There is an object flag inside of an exported Technology File that can be set to lock the constraints inside of Constraint Manager. By default, the object flag is present by default and set to the "NOTReadOnly" setting.
Here is an example of what the object flag looks like:
It is a pretty simply process:
1) Export the Technology file from inside of Constraint Manager using File > Export > Technology File.
2) Open the Technology file in a text editor and replace "fObjectNOTReadOnly" with "fObjectReadOnly".
3) Import the Technology file back into Constraint Manager using File > Import > Technology File.
Performing these steps will lock the Constraints in Constraint Manager and it will prevent making changes knowingly or unknowingly.
There is more information in the Cadence Help Documentation, just search for "Locking Constraint Sets".
Hope this helps,