How to disable SNMP service

Information shared by SNMP may be used to gain more knowledge about the remote host, or to change the configuration of the remote system (if the default community allows such modifications). If your don't monitor your LPAR via SNMP then best way to improve security is to disable SNMP service.
SNMP service can be disabled by this command

ENDTCPSVR *SNMP

This command will ensure that SNMP will not start again when TCP is restarted

CHGSNMPA AUTOSTART(*NO) ALWSNMPV3(*NO)

You can also configure specific SNMP Community

CFGTCPSNMP

 and then option

2. Work with communities for SNMP

with option 2=Change on specific Community

                     Change Community for SNMP (CHGCOMSNMP)                 
                                                                            
 Type choices, press Enter.                                                 
                                                                            
 Community name . . . . . . . . . > 'public'      Character value           
 Translate community name . . . . > *YES          *YES, *NO                 
 Manager internet address:                                                  
   Manager internet address . . .   *ANY                                    
                                                                            
   Manager internet address mask                                            
                                                                            
                + for more values                                           
 Object access  . . . . . . . . .   *NONE         *SAME, *SNMPATR, *READ... 
 Log set requests . . . . . . . .   *NO           *SAME, *SNMPATR, *YES, *NO
 Log get requests . . . . . . . .   *NO           *SAME, *SNMPATR, *YES, *NO

Object access can have any of this values

*SAME   
*SNMPATR
*READ   
*WRITE  
*NONE