Which kind of BRMS deployer are you using?
1). Deployable (EAP 6) (176 MB)
2). Installer (250 MB) JAR https://www.jboss.org/download-manager/file/jboss-brms-6.2.0.GA-installer.jar
If you are using JAR installer then please run it as following (with Heap defined at installation level):
java -Xms1024m -Xmx1024m -jar jboss-brms-6.2.0.GA-installer.jar