Oracle Flashback Table and Amazon Aurora PostgreSQL snapshots

With Amazon DMS, you can migrate databases between different database platforms or versions by capturing consistent data snapshots from the source database and applying them to the target database. Oracle Flashback Table and Amazon Aurora PostgreSQL snapshots provide point-in-time backups of the source database, enabling migration with minimal downtime.

Oracle usage

Oracle Flashback Table is a data protection feature used to undo changes to a table and rewind it to a previous state (not from backup). While Flashback table operations are running, the affected tables are locked, but the rest of the database remains available.

If the structure of a table has been changed since the point of restore, the FLASHBACK will fail. Row movement must be enabled.

The data to restore must be found in the undo (dba must manage the size and retention). A table can be restored to an System Change Number (SCN), Restore Point, or Timestamp.

Examples

Flashback a table using SCN (query V$DATABASE to obtain the SCN).

SELECT CURRENT_SCN FROM V$DATABASE;
FLASHBACK TABLE employees TO SCN 3254648;

Flashback a table using a Restore Point (query V$RESTORE_POINT to obtain restore points).

SELECT NAME, SCN, TIME FROM V$RESTORE_POINT;
FLASHBACK TABLE employees TO RESTORE POINT employees_year_update;

Flashback a table using a Timestamp (query V$PARAMETER to obtain the undo_retention value).

SELECT NAME, VALUE/60 MINUTES_RETAINED
FROM V$PARAMETER
WHERE NAME = 'undo_retention';
FLASHBACK TABLE employees TO
TIMESTAMP TO_TIMESTAMP('2017-09-21 09:30:00', 'YYYY-MM-DD HH:MI:SS');

For more information, see Backup and Recovery User Guide in the Oracle documentation.

PostgreSQL usage

Snapshots are the primary backup mechanism for Amazon Aurora databases. They are extremely fast and nonintrusive. You can take snapshots using the Amazon RDS Management Console or the Amazon CLI. Unlike RMAN, there is no need for incremental backups. You can choose to restore your database to the exact time when a snapshot was taken or to any other point in time.

Amazon Aurora provides the following types of backups:

Examples

For examples, see PostgreSQL Amazon Aurora Snapshots.

Summary

CREATE RESTORE POINT
  before_update GUARANTEE
  FLASHBACK DATABASE;

aws rds create-db-cluster-snapshot
  --db-cluster-snapshotidentifier Snapshot_name
  --db-cluster-identifier Cluster_Name

ALTER SYSTEM SET
  db_flashback_retention_target=2880;

shutdown immediate;
startup mount;
flashback database to
  restore point before_update;

aws rds restore-db-cluster-from-snapshot
  --db-cluster-identifier NewCluster
  --snapshot-identifier SnapshotToRestore
  --engine aurora-postgresql

aws rds create-db-instance
  --region us-east-1
  --db-subnetgroup default
  --engine aurora-postgresql
  --db-cluster-identifier clustername-restore
  --db-instance-identifier newinstance-nodeA
  --db-instance-class db.r4.large

shutdown immediate;
startup mount;
FLASHBACK DATABASE TO TIME
  "TO_DATE ('01/01/2017','MM/DD/YY')";

aws rds restore-db-cluster-to-point-in-time
  --db-cluster-identifier clustername-restore
  --source-db-cluster-identifier clustername
  --restore-to-time 2017-09-19T23:45:00.000Z

aws rds create-db-instance
  --region us-east-1
  --db-subnetgroup default
  --engine aurora-postgresql
  --db-cluster-identifier clustername-restore
  --db-instance-identifier newinstance-nodeA
  --db-instance-class db.r4.large

For more information, see rds in the CLI Command Reference and Restoring a DB instance to a specified time and Restoring from a DB snapshot in the Amazon RDS user guide.