Hello Vijay,
I don't think you need to shutdown the system, but note the following :
- Time zones on mainframe can be set on LPAR level only
- It is not possible to set different time zones for different databases running on the same LPAR
- It is required to run database and application servers in the same time zone (see DBA guide)
https://service.sap.com/~sapidb/011000358700000275902011E.PDF
- It is required to have identical time zones for the application servers and SAP system time (see note 198411)
- Time zone can be changed for individual users in SU01 (or by the user
himself)
Links to IBM documentations: http://scn.sap.com/docs/DOC-8237
Regards,
Javier