General

Specific attention was paid to the configuration of the ISFC logical link connecting the two z/VM® members.

In general, the z/VM recommendations given in z/VM CP Planning and Administration, chapter Planning the ISFC Network in an SSI Cluster and those given in the IBM® z/VM Performance Report (see Live Guest Relocation and ISFC Improvements) were followed. However, if necessary for the investigation of corner cases of the ISFC logical link configurations, some of the guidelines were not applied.

An ISFC logical link connecting two z/VM members is configured by selecting up to sixteen FCTC connections. These FCTC connections must have been previously configured in the IOCDS (IOCDS configuration for FICON CTCs), such that each FCTC connection in turn connects the two LPARs hosting the z/VM members.

For example, if the FCTC device with device number D000 is configured in the z/VM member running in LPAR1 and for the ISFC logical link connecting to LPAR2, then the corresponding FCTC device (the other "end" of the FCTC connection) must in turn be configured in the z/VM member running in LPAR2 and for the ISFC logical link connecting to LPAR1. In addition, both FCTC devices must have been previously configured in the IOCDS as an FCTC connection connecting LPAR1 with LPAR2.

Each side of an ISFC logical link is configured separately by ACTIVATE ISLINK statements in the z/VM system configuration file, by executing ACTIVATE ISLINK privileged CP commands, or both. Either way, ACTIVATE ISLINK requires the FCTC device number(s) as parameter(s). The use of CP commands provides for the ability to dynamically modify the actual configuration of ISFC logical links after IPL.

Once one or more respectively prepared FCTC devices pairs are configured for an ISFC logical link on both of its sides, the z/VM members connected through the ISFC logical link can use the link for communication and data transfer; this includes the case of transporting the data resulting from virtual machines being relocated from one z/VM member to the other.

In the test environment, the z/VM system configuration file contained an initial configuration for the ISFC logical link between the two z/VM members that became effective at IPL time. Then, during the preparation phase of each test case, the ISFC logical link was dynamically reconfigured, thereby establishing the test specific ISFC logical link configuration requirements.