To retain information that's available in the cache, you must run the MicroTx transaction coordinator in maintenance mode before upgrading it. When you run the MicroTx transaction coordinator in maintenance mode, it copies the cached maintenance data to the data store. Data is stored in the cache only when you enable caching for the MicroTx coordinator and when you use Oracle Database or etcd as data store. You can not enable caching if you use internal memory as the transaction store.