For documentation, is this an "across the board" option for all of our possible DBs, or does it pertain to just particular servers/vendors?

The "Write Only" option would only require us to add a .isWriteOnly() check in these areas :

1) Query Window : Execute -> If it is a SELECT statement.
2) Query Builder : Execute -> All the time, because it is always a SELECT statement.

We can't do the check in a Thread, so we need to do the check in :

1) QueryPanel.java line 4779
2) QueryBuilderFrame.java line 460.

We only want to do the check if the server is write only.  So, we need to use the condition : ConnectionProperties.isWriteOnly().  If it is true then use AFScriptContextUtil.checkForSelect() which needs to be implemented based on .checkPermission().

Now checks in QB and QA(Select only) when write only is turned on. Should we do this for read only??

I selected Mode=Write Only and Entered Warning Message=This Server is Write Only. As in the attached screenshot, we have No / Yes button, which seems to be a bit out of context. In the Title of the dialog, do you want to add ?

Select Warnings. Do you wish to proceed ?

1. If user has warning message set, then tries to execute a query, the dialog pops up. If you click on the X button to close the dialog, the query executes. Is this intended behavior ?

2. Do we need to extend this to the Table Data Editor as well ?

There is an option to set a custom message for a "Read Only" server.  But for "Write Only" I think we should have a fixed message.  This is the message we should use "This server is marked as a Write Only Data Warehouse.  Would you like to proceed?"

If the user clicks "X" or hits ESC then it should not proceed.