Hi Raghunath,
Upgrading the SAPJVM is never a good option and it is recommended to never update it manually.All the servers runs on the Custom created Java provided by SAP which is SAPJVM. If you wanted to upgrade the Java you can upgrade the Server.
You can check the below KBA to check which SAPJVM is provided with Bundled Service Packs :
2112338 - List of Tomcat and JVM versions shipped with each (support pack) SP of SAP BusinessObjects 4.x
Regards,
Mahak