RMAN backup basics: ARCHIVELOG mode, a nightly backup script and restore

RMAN (Recovery Manager) is Oracle’s built-in backup tool. It reads data files block by block, records every backup in the control file (or a recovery catalog) and knows which backups it needs for a restore. Commands below are from the Oracle Database 19c documentation and run the same way in later releases.

1. Check and enable ARCHIVELOG mode

To back up an open database and recover to any point in time, the database must run in ARCHIVELOG mode, where filled online redo logs are copied to archived logs. In NOARCHIVELOG mode you can only back up a closed, consistent database.

sqlplus / as sysdba
SQL> ARCHIVE LOG LIST
SQL> SELECT log_mode FROM v$database;

Warning: switching modes needs a restart, so plan downtime. Make sure archived logs have a destination with enough space (a fast recovery area or LOG_ARCHIVE_DEST_1). The database must be mounted but not open:

SQL> SHUTDOWN IMMEDIATE
SQL> STARTUP MOUNT
SQL> ALTER DATABASE ARCHIVELOG;
SQL> ALTER DATABASE OPEN;
SQL> ARCHIVE LOG LIST

Take a full backup right afterwards: the documentation states that backups taken in NOARCHIVELOG mode cannot be used together with the new archived logs. In a CDB this is done once for the whole CDB, connected to the root.

2. One-time RMAN configuration

rman target /

RMAN> SHOW ALL;
RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS;
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;

A recovery window of 7 days keeps whatever is needed to recover to any time in the last week; the default policy is REDUNDANCY 1. Control file autobackup is on by default for CDBs with COMPATIBLE 12.2 or higher, but setting it explicitly does no harm: without a control file backup, a restore onto a new server is much harder. Backups go to the fast recovery area unless you configure another disk location with CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT ....

3. The nightly script

The script writes an RMAN command file, runs it with operating-system authentication and keeps a log per run. Run it as the Oracle software owner on the database server.

#!/usr/bin/env bash
# rman-backup.sh - nightly RMAN backup of the whole CDB plus archived redo logs.
# Run as the oracle software owner. License: CC0-1.0
set -euo pipefail

export ORACLE_SID="${ORACLE_SID:-ORCLCDB}"
export ORACLE_HOME="${ORACLE_HOME:?set ORACLE_HOME}"
export PATH="$ORACLE_HOME/bin:$PATH"
export NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'

LOG_DIR="${LOG_DIR:-/home/oracle/rman-logs}"
KEEP_LOG_DAYS="${KEEP_LOG_DAYS:-30}"

mkdir -p "$LOG_DIR"
stamp="$(date +%Y%m%d-%H%M%S)"
logfile="$LOG_DIR/rman-${ORACLE_SID}-${stamp}.log"
cmdfile="$(mktemp)"
trap 'rm -f "$cmdfile"' EXIT

cat > "$cmdfile" <<'EOF'
CONNECT TARGET /
SHOW RETENTION POLICY;
BACKUP DATABASE PLUS ARCHIVELOG;
CROSSCHECK BACKUP;
DELETE NOPROMPT OBSOLETE;
LIST BACKUP SUMMARY;
EXIT;
EOF

if rman @"$cmdfile" > "$logfile" 2>&1 && ! grep -q 'RMAN-' "$logfile"; then
  echo "RMAN backup OK: $logfile"
  status=0
else
  echo "RMAN backup FAILED, see $logfile" >&2
  grep -E 'RMAN-|ORA-' "$logfile" | head -n 20 >&2 || true
  status=1
fi

find "$LOG_DIR" -maxdepth 1 -type f -name 'rman-*.log' -mtime +"$KEEP_LOG_DAYS" -delete
exit "$status"

• BACKUP DATABASE PLUS ARCHIVELOG backs up all data files plus the archived redo logs, so the backup can be made consistent during recovery. Run against the root of a CDB, it covers the root and all PDBs.
• CROSSCHECK BACKUP marks backups whose files have disappeared as EXPIRED.
• DELETE NOPROMPT OBSOLETE removes backups the retention policy no longer needs. NOPROMPT skips the confirmation question.
• The script treats any RMAN- message in the log as a failure, which can include warnings. Review those and adjust the check if a warning is expected in your setup.

# crontab of the oracle user
0 1 * * * ORACLE_HOME=/u01/app/oracle/product/19.0.0/dbhome_1 ORACLE_SID=ORCLCDB /home/oracle/bin/rman-backup.sh

Archived logs pile up between full backups. On busy systems add a separate job several times a day with BACKUP ARCHIVELOG ALL DELETE INPUT;, which backs up archived logs and then deletes the copies it backed up. For a single PDB, connect to the root and run BACKUP PLUGGABLE DATABASE orclpdb1;. For large databases, look at incremental backups (BACKUP INCREMENTAL LEVEL 0 DATABASE once, then level 1); note that a plain full backup cannot serve as the level 0 base.

4. Check that backups are usable

RMAN> LIST BACKUP SUMMARY;
RMAN> REPORT OBSOLETE;
RMAN> RESTORE DATABASE PREVIEW SUMMARY;
RMAN> RESTORE DATABASE VALIDATE;

RESTORE ... VALIDATE reads the backups as if restoring them, without writing any data files. Run it regularly; a backup that has never been tested is a hope, not a backup.

5. Restore and recover (concept)

Warning: STARTUP FORCE MOUNT aborts the running instance, and RESTORE DATABASE overwrites the current data files. Practise on a test server, and before touching production check with RESTORE DATABASE PREVIEW which backups would be used.

rman target /

RMAN> STARTUP FORCE MOUNT;
RMAN> RESTORE DATABASE;
RMAN> RECOVER DATABASE;
RMAN> ALTER DATABASE OPEN;

RESTORE copies data files back from the backup; RECOVER applies archived and online redo to bring them forward to the latest committed state. Recovering to an earlier time (point-in-time recovery) and restoring single tablespaces or PDBs follow the same restore-then-recover idea with extra clauses described in the Backup and Recovery User’s Guide.

Official documentation

• Oracle Database 19c Administrator’s Guide: Managing archived redo log files
• Oracle Database 19c Backup and Recovery: Getting started with RMAN
• Oracle Database 19c Backup and Recovery: Backing up the database