How Weblogic Starts??

There is a startup script startWeblogic.sh under ${DOMAINHOME}. This script calls another startWebLogic.sh under ${DOMAINHOME}/bin. Under ${DOMAINHOME}/bin, there are also other configuration scripts setDomainEnv.sh, startManagedWebLogic.sh, etc. Commonly we will call startWebLogic.sh in DOMAINHOME to start the WLS admin server.
Startup then proceeds with these steps:
The DOMAINHOME environment variable is set.
The script calls ${DOMAINHOME}/bin/startWebLogic.sh.

${DOMAINHOME}/bin/startWebLogic.sh calls ${DOMAINHOME}/bin/setDomainEnv.sh.

setDomainEnv.sh calls ${WL_HOME}/common/bin/commEnv.sh. commEnv.sh sets a series of common environment variables, none of which are directly related to the particular domain: for example, WL_HOME, JVM memory options, other JVM parameters, and system properties. These variables are set for use by any WebLogic Server domains, as well as system utilities like Node Manager, etc. A particular domain can (and usually does) override these settings, so setting them here may not actually change the settings for your particular domain. It probably will impact the settings for Node Manager, however.

After commEnv.sh is executed, setDomainEnv.sh will set other memory parameters and variables. In fact, the settings from commEnv.sh are overridden here.

After setDomainEnv.sh completes, the system returns to ${DOMAINHOME}/bin/startWebLogic.sh, organizes the parameters, and calls java to start up the JVM and start WebLogic Server.

If we want to change the default memory parameters, the best location is in startWebLogic.sh or setDomainEnv. For example, in setDomainEnv.sh, modify the WLS_MEM_ARGS_32BIT from “-Xms512m -Xmx512m” to “-Xms1024m -Xmx1024m”