The message "CA XCOM Data Transport r11.6 SP01 (64-Bit) is already installed on your system. The existing version needs to be uninstalled first before the installation can start. The installation will exit now" implies that the registry values are corrupted.
The last steps of the initial installation which are displayed on console might have been missed:
and xcomqm -r was issued too soon and the original installation was probably successful.
After uninstalling and then trying to do a new install, it appears, a registry file was probably left behind. To clear the corrupted registry entry:
Remove or rename the registry file /var/.com.zerog.registry.xml and do the new install.