You will likely need to bounce application services for this setting to take effect
You would need to pass xauth list in order to make Display/xclock work.
You can follow the below steps (assuming you would be having root access, else check with your OS team):
1. Login to root and check if xclock works here by following below:
2. The pass "xauth list" and note down the below:
You'll get something like
host.domain:10 mit-magic-cookie-1 4d22408a71a55b41ccd1657d377923ae
3. Login to app id (OS user/ app user) and pass:
xauth add <entire output of above xauth list>
4, Then try xclock, it should be working by then.
Login as Root, open terminal in VNC and execute
Now try from applmgr
It should work fine.
Note: Make sure display value has been configured in contextfile .
<applmgr>$grep display $CONTEXT_FILE
<DISPLAY oa_var="s_display" osd="unix">Your Hostname:0.0</DISPLAY>