CA UIM REST Api disk qos data returns empty for QOS_DISK_USAGE

Document ID : KB000106005
Last Modified Date : 11/07/2018
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While trying to use the Unified Infrastructure Manager REST Web Services API to see Disk Usage Percentage for several hosts, a 400 error is returned (indicating a BAD URL path) or we get no data.
This only seems to happen when we URL encode the directory slashes for Windows "\" or Unix/Linux "/".
UIM 8.5.1 SP1
webservices_rest 8.51
Here are examples showing the "Allow Backslash" encoding is not enabled:
Allow Backslash is not enabled

Here is an example showing the patch is needed OR the QOS_DISK_USAGE is not enabled:
QOS not enabled or patch is needed

Here is an example showing a working GET for QOS_DISK_USAGE:
Successful GET call of UIM Web Services to get QOS_DISK_USAGE - disk usage qos using Postman
1- Deploy webservices_rest 9.0 to the REST web services wasp robot
    This contains important fixes.
2- Validate "Allow Backslash" is enabled (see "Additional Information section below).
3- Ensure the QOS_DISK_USAGE or other QOS is enabled in the web adminconsoleapp.
Enabling QOS_DISK_USAGE in admin console

Additional Information:
Allow Backslash Encoding

(Optional) Enable Slash Characters
The default configuration of the Tomcat server that serves as the platform for UMP does not allow encoded forward-slash characters (“/”) or backward-slash characters ("\") in URLs. To avoid problems (for example, when requesting QoS metrics that contain a slash in the name), you will have to add an extra Java startup object to the wasp probe.
Follow these steps:

1- Open the wasp configuration GUI.
2- Click the wasp node.
3- Enter the following argument in the Extra JVM arguments field.
-Dfile.encoding=UTF8 -Dorg.apache.tomcat.util.buf.UDecoder.ALLOW_ENCODED_SLASH=true -Dorg.apache.catalina.connector.CoyoteAdapter.ALLOW_BACKSLASH=true
Tip: The parameters in the Extra JVM arguments field are separated by spaces. The screen capture below shows what the Extra JVM arguments field looks like when more than one parameter is defined: 
Wasp configuration showing Allow Backslash