We are running a z9BC with z/VM 5.4. Prior to the microcode upgrade a week ago Saturday, our OS/390 guest used native OSA addresses and our z/OS guests (1.4 & 1.5) used a VSWITCH. After the microcode upgrade, our OS/390 guest (using native OSA addresses) was communicating very slowly with a TN3270 terminal. We also tested one of our z/OS (1.4) guests using native OSA addresses and communication with a TN3270 terminal was also very slow. When I put the z/OS (1.4) guest back to using the VSWITCH, everything is fine. The microcode level is 67.
Over a year ago, we replaced the OSA card because of another problem. Is the OSA card having problems ? Is the VSWITCH doing something to make older operating systems work ?
