Platform MBean Server Used

For you to find "Platform MBean Server Used" and enable it. The weblogic version has to be 10.3.3 or above.
For lower versions: us the below method.

1. start your weblogic admin and open the console.
2, invoke *\wlserver_10.3\common\bin wlst.cmd or wlst.sh
3.
If you have configured SSL run below, else move to step 4
java -Dweblogic.security.SSL.ignoreHostnameVerification=true -Dweblogic.security.TrustKeyStore=DemoTrust weblogic.WLST
4.
wls:/offline> connect()
Please enter your username [weblogic] :weblogic
Please enter your password [welcome1] :
Please enter your server URL [t3://localhost:7001] :
wls:/base_domain/edit> startEdit()
wls:/base_domain/edit !> cd ('JMX')
wls:/base_domain/edit/JMX !> ls()
drw-   base_domain
wls:/base_domain/edit/JMX !> cd ('base_domain')
wls:/base_domain/edit/JMX/base_domain !> ls()

-rw-   CompatibilityMBeanServerEnabled              true
-rw-   DomainMBeanServerEnabled                     true
-rw-   EditMBeanServerEnabled                       true
-rw-   InvocationTimeoutSeconds                     0
-rw-   ManagementEJBEnabled                         true
-rw-   Name                                         base_domain
-rw-   Notes                                        null
-rw-   PlatformMBeanServerEnabled                   false
-rw-   PlatformMBeanServerUsed                      false
-rw-   RuntimeMBeanServerEnabled                    true
-r--   Type                                         JMX

-r-x   freezeCurrentValue                           Void : String(attributeName

-r-x   isSet                                        Boolean : String(propertyName)
-r-x   restoreDefaultValue                          Void : String(attributeName

-r-x   unSet                                        Void : String(propertyName)

wls:/base_domain/edit/JMX/base_domain !> cmo.setPlatformMBeanServerUsed(true)
wls:/base_domain/edit/JMX/base_domain !> save()
Saving all your changes ...
Saved all your changes successfully.
wls:/base_domain/edit/JMX/base_domain !> exit()

For 10.3.5 and above you can simply do the below

1.) Set the Platform MBean Server Enabled from Admin Console Domain >Configuration > General >Advanced >Platform MBean Server Enabled

2.) Enable this system property in server startup scripts

-Djavax.management.builder.initial=weblogic.management.jmx.mbeanserver.WLSMBeanServerBuilder

 ref: http://download.oracle.com/docs/cd/E14571_01/web.1111/e13728/understandwls.htm#JMXCU239