Could not reserve enough space for object heap

During oracle 12C agent installation i got below,, here is fix , i will add more detail on this ..

Unzipping the agentcoreimage.zip to /export/apps/oradba/XXXX/agent125c_new ....
12.1.0.5.0_PluginsOneoffs_23.zip
Executing command : /export/apps/oradba/XXXX/agent125c/unzip -o /export/apps/oradba/XXXX/agent125c/12.1.0.5.0_PluginsOneoffs_23.zip -d /export/apps/oradba/XXXX/agent125c_new
Successfully unzipped /export/apps/oradba/XXXX/agent125c/12.1.0.5.0_PluginsOneoffs_23.zip to /export/apps/oradba/XXXX/agent125c_new !
mv: cannot rename /export/apps/oradba/XXXX/agent125c_new/sbin_new to /export/apps/oradba/XXXX/agent125c_new/sbin/sbin_new: File exists
Executing command : /export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/jdk/bin/java  -d64 -classpath /export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/oui/jlib/OraInstaller.jar:/export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/oui/jlib/xmlparserv2.jar:/export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/oui/jlib/srvm.jar:/export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/oui/jlib/emCfg.jar:/export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/jlib/agentInstaller.jar:/export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0/oui/jlib/share.jar oracle.sysman.agent.installer.AgentInstaller /export/apps/oradba/XXXX/agent125c_new/core/12.1.0.5.0 /export/apps/oradba/XXXX/agent125c /export/apps/oradba/XXXX/agent125c_new /export/apps/oradba/XXXX/agent125c_new/agent_inst AGENT_BASE_DIR=/export/apps/oradba/XXXX/agent125c_new
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

After export below parameter my agent went fine..  

export _JAVA_OPTIONS='-Xms64M -Xmx128m'