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
READONLYmode are executed automatically after the switch. - Node to run on: Any single Coordinator node is enough.
-
Privileges: Only the
gbaseuser 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 gbase database.
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