setting db_cache_size when using automatic sga management

**Here is my scenario on a Oracle 10.2.0.4 on solaris 10.

sga_max_size set at 6G
db_cache_size at 3G
sga_target -0 - disabled

and during certain time I observe the cache hit ratio goes to 60% . I am planning to enable ASMM as below

sga_max_size - 8G
db_cache_size -3G
sga_target - 6G

so will oracle extend the db_cache_size to maintain a better hit ratio ? will it work ?

but again anybody has any experience with this bug which crashes the instance when we have ASMM enabled and then setting up manually a db_cache_size .
*Ora-00600: [Kmgs_pre_process_request_2] after having adjusted db_cache_size
[ID 737458.1]

 Appreciate any recommendation here

thanks in advance
Kart

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