It worked after doing below steps:
1. Reinstalled 1.6.0_07 64 bit jdk.
2. added -d64 to asadmin script
3. added <jvm-options>-d64</jvm-options> to domain.xml
4. Changed <jvm-options>-client</jvm-options> to <jvm-options>-server</jvm-options>
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