The wrapper.conf file is used to set the minimum and maximum heap size for each Mule application server. The wrapper.conffile should be located at mule_home/server_name/conf/wrapper.conf.
The wrapper.java.maxmemory options is used to specify the maximum amount of memory that can be allocated for heap space, in MB. The wrapper.java.initmemory option is used to specify the initial (aka minimum) amount of memory to be allocated for heap space, in MB.
If you change the minimum or maximum heap size, you will need to restart the application server for the change to take effect.