I am using APEX4.2 to produce a graph ( by AnyChart) and used the simple pop up windows to save the graph to a PNG image file called test.png in the windows location ( being X:\APEX_CHART where X is pointing to windows server /abc/Transfer/APEX_CHART/ ).
That doesn't look like a Windows path. Do you mean \\abc\Transfer\APEX_CHART?
Now I wanted to be able to change the permission of this windows file to be private to one group and not available to other public users. Can I achieve this via API from Oracle PL/SQL ?
Is the database on the same server as \\abc\Transfer\APEX_CHART?
I may be wrong and other may know better but I very much doubt that that would be possible.
To do so would require that the browser have file permissions over the client OS. I for one would be very nervous if I opened up a website and it had admin rights to my file system.
That would indeed be a serious security issue, and there is no way the browser should be able to do so. However it may be possible (if also not very advisable) if the target location is accessible by the database server.