GBase 8a Backup and Recovery Guide: gcrcman from Basics to Production

GBase 8a, as an MPP analytical database, does not use WAL transaction logs. Instead, it relies on the dedicated gcrcman tool for snapshot backups. This guide covers cluster‑level, database‑level, and table‑level backup/recovery, along with scheduling strategies and common issues. 1. gcrcman Fundamentals GBase 8a omits transaction logs for maximum scan throughput, so point‑in‑time recovery is not supported. You must use gcrcman for periodic snapshots. The tool is located at $GCLUSTER_BASE/server/bin/gcrcman.py . Backup Types Scope Full (level 0) Incremental (level 1) Online? Cluster ✅ ✅ ❌ (switch to readonly) Database ✅ ✅ ❌ (switch to readonly) Table ✅ ✅ ✅ (locks the table only) Cycle and Point Model A full backup starts a new cycle; subsequent incrementals continue the same cycle. You can restore to any snapshot by specifying cycle_id and point_id . 2. Pre‑Backup Checks # 1. Cluster must be ACTIVE gcadmin # 2. All nodes must have synchronized time (drift < 1 second) date # 3. Create backup directory on every node mkdir -p /data/backup/gbase8a chown gbase:gbase /data/backup/gbase8a # 4. Verify pexpect is available python -c "import pexpect; print('OK')" # If missing, copy it from the installation package cp $GCLUSTER_BASE /../gcinstall/pexpect.py $GCLUSTER_BASE /server/bin/ Do not place backup directories under $GCLUSTER_BASE , $GBASE_BASE , or $GCWARE_BASE . 3. Cluster‑Level Backup and Recovery Full Backup # 1. Switch to readonly mode gcadmin switchmode readonly gcadmin # verify READONLY # 2. Run full backup interactively python $GCLUSTER_BASE /server/bin/gcrcman.py \ -d /data/backup/gbase8a \ -p your_db_password gcrcman> backup level 0 gcrcman> exit # 3. Switch back to normal gcadmin switchmode normal Incremental Backup (requires a prior full backup) gcadmin switchmode readonly python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> backup level 1 gcrcman> exit gcadmin switchmode normal View Backup History python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> show backup Cluster‑Level Recovery # 1. Switch to recovery mode gcadmin switchmode recovery # 2. Restore to the latest point, or to a specific cycle/point python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> recover # latest gcrcman> recover 0 # last point of cycle 0 gcrcman> recover 0 1 # point 1 of cycle 0 gcrcman> exit # 3. Restart gcware (as root) service gcware restart # 4. Switch back to normal gcadmin switchmode normal ⚠️ Recovery rolls the entire cluster back to the snapshot. All data written after the backup point is lost. 4. Table‑Level Backup and Recovery Table‑level backups only lock the target table, making them ideal for online production use. Full and Incremental Table Backup python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> backup table sales_db.orders level 0 # full gcrcman> backup table sales_db.orders level 1 # incremental gcrcman> exit Table‑Level Recovery (no cluster state change needed) python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> recover table sales_db.orders # latest point gcrcman> recover table sales_db.orders 0 1 # specific point gcrcman> exit 5. Cleaning Up Expired Backups python $GCLUSTER_BASE /server/bin/gcrcman.py -d /data/backup/gbase8a -p password gcrcman> show backup gcrcman> delete 0 # Delete cycle 0 (keep at least one complete cycle) gcrcman> clean # Remove orphaned files from interrupted backups gcrcman> exit 6. Production Scheduling Recommended cadence : Cluster full backup weekly on Sunday, daily incremental, important tables backed up daily. Sample automation script (registered in cron): #!/bin/bash BACKUP_DIR = /data/backup/gbase8a DB_PASS = your_db_password LOG_FILE = /home/gbase/logs/backup_ $( date +%Y%m%d ) .log GCRCMAN = $GCLUSTER_BASE /server/bin/gcrcman.py DOW = $( date +%u ) if [ " $DOW " -eq 7 ] ; then LEVEL = 0 else LEVEL = 1 fi gcadmin switchmode readonly >> $LOG_FILE 2>&1 python $GCRCMAN -d $BACKUP_DIR -p $DB_PASS << EOF >> $LOG_FILE 2>&1 backup level $LEVEL exit EOF BACKUP_STATUS = $? gcadmin switchmode normal >> $LOG_FILE 2>&1 if [ $BACKUP_STATUS -eq 0 ] ; then echo "[ $( date ) ] Backup succeeded" >> $LOG_FILE else echo "[ $( date ) ] Backup failed!" >> $LOG_FILE exit 1 fi Crontab entry for the gbase user: 0 2 * * * /home/gbase/scripts/daily_backup.sh 7. After Scaling or Replacing Nodes Old backups are unusable after topology changes. Immediately run a new full backup (level 0) to start a new cycle. 8. Common Issues Another gcrcman process is running : Check with gcadmin showlock . If a stale lock remains, ask a DBA to evaluate and clean it. Disk full during backup : A full backup needs ~1.2× the data directory size; an incremental needs ~1.5× the change volume. Restored data doesn't match expectations : Cluster‑level recovery rolls back everything. If you only dropped a single table, use table‑level recovery