In CICS® DA terms, a model is a collection of all the system information that is identified when the CICS DA discovery process is run against a sysplex. The model is maintained by the CICS DA server. You can load a copy of the model into your local workspace and use the CICS DA client to visualize and understand your CICS environment. The same model can be loaded by multiple users.
Any changes that you, or any other users, make to the local model are also applied to the model on the server. If a user reloads the model on their machine, then they see the changes that you made. Similarly, if you reload the model, then you see any changes that other users made.
There is no file-locking in place for the model, so it is possible for two or more users to attempt to update the model at the same time. This can mean that the local model becomes out of sync with the server model. If the models are out of sync, you might get an error message next time that you do an action to the model. Alternatively, you might have other symptoms, such as the text <missing names> showing instead of the model element name in the model tree, or Unknown status showing in the visualization views.
If you see either of these symptoms, or you have other problems with the model, reload the model on your machine. If you still see the symptoms, run a new discovery and reload the new model.
When discovery runs, the existing server model is not deleted, so all tags and start polices are retained. Any new elements that are discovered are added to the existing model.