_ksm_granule_size is the lowest particle size size. If SGA_MAX_SIZE is less than 128m, _ksm_granule_size is 4m; if SGA_MAX_SIZE is greater than or equal to 128M, then _ksm_granule_size is 8m
_ksm_granule_size determines the size of other parameters.
If the SGA_MAX_SIZE is 64m, then _ksm_granule_size is 4m, then if the db_cache_size is 9m, the actual db_cache_size will be set to 12m because the lowest particle size is 4m;
If the SGA_MAX_SIZE is 128m, then _ksm_granule_size is 8m, then if the db_cache_size is 9m, the actual db_cache_size will be set to 16m because the lowest particle size is 8m;
