"Unknown command" seems to be from MySQL, so the pool setup is not complete.
You can refer the basic configuration required for MySQL at :
GLASSFISH_INSTALL_ROOT/lib/install/templates/resources/jdbc/mysql_type4_datasource.xml
If it still fails :
you can set FINEST log level :
asadmin set-log-levels javax.enterprise.resource.resourceadapter=FINEST
and do a ping-connection-pool which might give more clues in GLASSFISH_INSTALL_ROOT/domains/<domain>/logs/server.log You can post the same.
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