GBase 8a Cluster Modes: NORMAL, READONLY, and RECOVERY Explained

GBase 8a MPP Cluster provides three operating modes that control what SQL operations are allowed: NORMAL, READONLY, and RECOVERY. Administrators switch between them manually to match the current operational need — from everyday production to maintenance windows and disaster recovery.

The Three Modes at a Glance

Mode	Allowed SQL	Forbidden SQL	Purpose
NORMAL	Everything: SELECT, DML, DDL, LOAD DATA	Nothing	Day‑to‑day production with full read/write capability.
READONLY	SELECT queries only	All writes: DML, DDL, LOAD DATA	Safe maintenance window — freezes data while keeping queries running.
RECOVERY	Nothing (not even SELECT)	Everything	Extreme data protection during restore or critical repair.

When to Use Each Mode

NORMAL: Default Production Mode

The cluster serves all reads and writes. Major maintenance that could affect consistency or availability should not be performed in this mode.

READONLY: Standard Maintenance & Change Window

This is the go‑to mode for planned operations — effectively a "maintenance mode". Use it for:

• Scaling up/down: Prevents concurrent writes during data redistribution.
• Node replacement: The cluster can automatically or manually enter read‑only mode when swapping a failed node.
• Backups: Ensures a consistent data view for logical backups.
• Major application releases: Briefly freeze data while deploying.

RECOVERY: High‑Risk Repair Mode

Reserved for specific recovery scenarios and used only by senior administrators:

• Restoring a cluster or VC from backups.
• Disaster recovery drills.
• Fixing severe logical corruption by importing external repair data.

All connections and queries are rejected in this mode — business is completely interrupted.

Viewing and Switching Modes

Check the Current Mode

gcadmin showcluster vc vc1

Look for the VIRTUAL CLUSTER MODE field in the output.

Switch Modes Manually

# Set the entire cluster to read‑only
gcadmin switchmode readonly

# Set a specific VC to recovery mode
gcadmin switchmode recovery vc vc1

# Return to normal mode
gcadmin switchmode normal

Best Practices

Mode	Frequency	Business Impact	Rule of Thumb
NORMAL	Always on	None	Production runs with full features.
READONLY	Often (maintenance)	Queries unaffected; writes paused	Switch to read‑only before any change.
RECOVERY	Rarely	Full outage	Use recovery only at the foundation level.

• Always switch to READONLY before planned maintenance such as node changes or backups.
• RECOVERY mode is an "operating room" — notify stakeholders and have a rollback plan.
• Mode switches are fast, but schedule them during off‑peak hours when possible.

Using these three modes wisely keeps your gbase database safe and your maintenance operations smooth. It's a simple but powerful part of the GBASE cluster management toolkit.