Maintenance of a Standalone DB System

Oracle starts maintenance of a standalone DB system (with or without HeatWave cluster enabled) within two hours of the Maintenance window start time that you define for the DB system.

The maintenance of the DB system involves a short period of downtime. To reduce the downtime, use high availability DB systems. See High Availability.

The maintenance of a standalone DB system involves the following steps:

1. New resources are launched using the latest operating system and MySQL server.
2. Data is synchronized between the old and new systems.
3. If the DB system has a HeatWave cluster attached to it, the data in the HeatWave cluster is automatically recovered or reloaded. See HeatWave Cluster Data Recovery.
4. The DB System's endpoints are attached to the new resources and new connections are allowed.
   Note
   
   If any errors occur during the maintenance, the process stops, rolls back to the old DB system, and connections resume.

Depending on the DB system settings and configuration, one of the following maintenance techniques is used:

• Offline maintenance: the MySQL server is stopped and the storage is cloned to ensure data consistency between the old and new systems. The DB system remains inaccessible for reads and writes from the time the server is stopped until connections are permitted to the new system.
• Near-zero downtime maintenance: the MySQL server is not stopped, and data is replicated between the old and new systems to ensure data consistency. The system remains accessible for reads and writes during replication. When the new system is ready, a short period of downtime is imposed where connections are blocked on the old system and all transactions are applied to the new server. During this short downtime period, inbound replication channels are temporarily disabled. These channels automatically start running and replicating after maintenance is complete.

  Near-zero downtime maintenance is applied only if the following prerequisites are met:

  1. The requested MySQL upgrade is not a major version upgrade. See Major Version Upgrade.
  2. The DB system does not have a HeatWave cluster.
  3. The DB system does not have Read Replicas or a Read Endpoint.
  4. The value of the binlog_expire_logs_seconds variable in the DB system's configuration is greater than or equal to 3600. See Configuration Variables.
  5. The last maintenance operation on your DB system must not be a failed near-zero downtime maintenance.

  If any of these prerequisites are not met, offline maintenance is applied to the DB system.

  To minimize the downtime, schedule your maintenance window during a low workload period that does not coincide with large update operations. For more information, see Configuring DB System Maintenance.