As the following message is repeated in wasp.
Oct 21 12:12:00:123 WARN [http-bio-80-exec-10, com.nimsoft.udm.utilities.nimbus.UdmConnectionLookup] Waiting to obtain UDM database connection properties: (11) command not found, Received status (11) on response (for sendRcv) for cmd = 'getUdmDatabaseConnection' Retrying...
As well as message in udm_manager log such as
Exception establishing Datomic connection: :db.error/not-enough-memory (datomic.objectCacheMax + datomic.memoryIndexMax) exceeds 75% of JVM RAM.
It is a shortage of JVM memory size.