You can configure an instance of an SAP system for IPv6. It is not important whether the instance has type AS ABAP, AS Java, or ABAP+Java (Dual-Stack)
SAP recommends that either all or none of the instances belonging to an SAP system are configured for IPv6. Otherwise communication problems in the internal systems could occur. Refer to the network guide for further information.
Set the environment variable SAP_IPv6_ACTIVE =1 for the instance. If this variable is set at operating system level when the application server is started, this means the instance is IPv6-enabled and can also be reached through an IPv6 connection.
In this way, the component dispatcher, gateway, ICM, and so on “listen” to all local IPv4 and IPv6 addresses if they are not explicitly restricted. The host's corresponding IPv6 addresses are also considered for a host name during connection setup If both IPv4 and IPv6 addresses are maintained for a specific host, the IPv6 address is used. If in this case an IPv4 connection is set up for the desired host, the differentiation has to take place using various host names.
If the environment variable is not set or SAP_IPv6_ACTIVE =0, IPv6 is deactivated. Network communication through IPv6 is then not possible.
This environment variable is valid for both the AS ABAP and for the AS Java. For the AS Java, the system variable java.net.preferIPv6Addresses is set to true. The virtual machine has the same name resolution behavior, such as for creating TCP/IP services, as AS ABAP has (see also Java documentation http://java.sun.com/j2se/1.5.0/docs/guide/net/ipv6_guide/index.html).