Online Switch Between READONLY and NORMAL Mode in GBase 8a
During maintenance tasks like backup or inspection, you often need to switch a gbase database cluster to READONLY mode and back to NORMAL afterwards. This post shows how to perform the switch online with gcadmin — no downtime required. Tools and Prerequisites Tool : gcadmin , located on any Coordinator node. User : Must be the cluster installation user (default gbase ). Pre‑check : Ensure gcware services are running ( gcware_services status ). Scope : The mode change applies cluster‑wide; no need to repeat per node. Step‑by‑Step (READONLY → NORMAL) Step 1: Check the Current Mode # Cluster‑wide gcadmin showcluster # Specific VC in a multi‑VC environment gcadmin showcluster vc vc1 Look at the VIRTUAL CLUSTER MODE field. Proceed only if it shows READONLY . Step 2: Switch to Normal Read/Write Mode # Single VC or whole cluster gcadmin switchmode normal # Specific VC gcadmin switchmode normal vc vc1 The switch takes effect in seconds. The cluster synchronises the new mode to all nodes automatically — no process restart is needed. Step 3: Verify the Change Run gcadmin showcluster again. When VIRTUAL CLUSTER MODE shows NORMAL , the cluster is fully writable again. Production Notes Business impact : An online switch does not interrupt running read queries. Pending write operations queued during READONLY mode are executed automatically after the switch. Node to run on : Any single Coordinator node is enough. Privileges : Only the gbase user can switch modes. Reverse switch : To return to read‑only mode, use gcadmin switchmode readonly [vc vc_name] . Troubleshooting : If the command fails, check gcware service health and node status first, then retry. Companion Commands # Check all cluster processes gcluster_services all info gcware_services all info # View detailed VC information gcadmin showvc The mode‑switch mechanism in GBase 8a is built for high availability. Following the "verify → switch → re‑verify" workflow lets you change cluster modes safely and transparently in a g