Updating the OneAgent on Solaris is similar to the current way of updating the ActiveGates. You have to install the later version on top of the old one. Please keep in mind this note for standalone app updates:
"If you are upgrading Dynatrace OneAgent from version prior to v1.141, make sure to change the paths for Java and Apache instrumentation to point to the files mentioned above. Only those files will be automatically updated during the consecutive OneAgent upgrades."