Running the 9.1.x installer having the JDK/JRE 1.9.x the installer throws the error:
You have selected an incorrect 64-bit JRE path. Please select the correct path and continue
Java 9 is not supported for any Remedy applications at this point.
This is documented in our BMC SOLUTION AND PRODUCT AVAILABILITY AND COMPATIBILITY (SPAC)
Install the Java version 1.8.x (being the required minimal build_45)
Take into account the following article:
Remedy - Server - v.9.x Installers not recognizing Java Update as a valid version. Error:"Invalid 64-bit JRE version" or/and "Invalid 32-bit JRE version"
Remedy - ITSM/Server- How do Oracle Licensing Changes Affect BMC Products using Java 8?