You can use In session Personalization rules even when xDB is disabled. But make sure that
1. Xdb.Tracking.Enabled is set to true
2.Open the web.config file and in the <appSettings> section, in the <add key="exmEnabled:define" value="yes"/> setting, change the value to “no”
- Open the web.config file and in the
<appSettings>
section, in the<add key="exmEnabled:define" value="yes"/>
setting, change the value to “no” - Xdb.Tracking.Enabled is set to true.
Check https://doc.sitecore.com/developers/91/platform-administration-and-architecture/en/enable-disable-the-xdb-and-the-tracker.html for more info