As Alexis has already pointed out there is no need to migrate from SJSAS to Glassfish since they are the same - with the exception of some branding and their respective installer.
Thus your problems must be a result of your configuration. If both installations shall serve the same apps using the same virtual servers you might simply copy the domain.xml from your SJSAS installation's domain to the domain you are using in Glassfish. Make sure that there are no hard coded references to your domain directory or your installation directory. You can replace them with ${com.sun.aas.instanceRoot} or ${com.sun.aas.installRoot} respectively.
If you cannot do this because of different apps served by the servers you should at least look at the differences in the configurations. Performance related elements deal among others with the JVM args, JDBC connection pool configuration, listener configuration and thread pool configuration. You should compare these elements thoroughly.
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Wolfram Rittmeyer
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