4 Oracle Database High Availability Solutions for Unplanned Downtime

Oracle Database offers an integrated suite of high availability solutions that increase availability.

These solutions also eliminate or minimize both planned and unplanned downtime, and help enterprises maintain business continuity 24 hours a day, 7 days a week. However, Oracle's high availability solutions not only go beyond reducing downtime, but also help to improve overall performance, scalability, and manageability.

Outage Types and Oracle High Availability Solutions for Unplanned Downtime

Various Oracle MAA high availability solutions for unplanned downtime are described here in an easy to navigate matrix.

The following table shows how the features discussed in the referenced (hyperlinked) sections can be used to address various causes of unplanned downtime. Where several Oracle solutions are listed, the MAA recommended solution is indicated in the Oracle MAA Solution column.

Table 4-1 Outage Types and Oracle High Availability Solutions for Unplanned Downtime

Outage Scope	Oracle MAA Solution	Benefits
Site failures	Oracle Data Guard and Enabling Continuous Service for Applications (MAA recommended)	Integrated client and application failover Fastest and simplest database replication Supports all data types Zero data loss by eliminating propagation delay Oracle Active Data Guard Supports read-only services and DML on global temporary tables and sequences to off-load more work from the primary Allows small updates to be redirected to the primary enabling read-mostly reports to be offloaded to standby Database In-Memory support
	Oracle GoldenGate	Flexible logical replication solution (target is open read/write) Active-active high availability (with conflict resolution) Heterogeneous platform and heterogeneous database support Potential zero downtime with custom application failover
	Recovery Manager, Zero Data Loss Recovery Appliance and Oracle Secure Backup	Fully managed database recovery and integration with Oracle Secure Backup Recovery Appliance provides end-to-end data protection for backups reduces data loss for database restores Non-real-time recovery
Instance or computer failures	Oracle Real Application Clusters and Oracle Clusterware and Enabling Continuous Service for Applications (MAA recommended)	Integrated client and application failover Automatic recovery of failed nodes and instances Lowest application brownout with Oracle Real Application Clusters
	Oracle RAC One Node and Enabling Continuous Service for Applications	Integrated client and application failover Online database relocation migrates connections and instances to another node Better database availability than traditional cold failover solutions
	Oracle Data Guard and Enabling Continuous Service for Applications	Integrated client and application failover Fastest and simplest database replication Supports all data types Zero data loss by eliminating propagation delay Oracle Active Data Guard Supports read-only services and DML on global temporary tables and sequences to off-load more work from the primary Allows small updates to be redirected to the primary enabling read-mostly reports to be offloaded to standby Database In-Memory support
	Oracle GoldenGate	Flexible logical replication solution (target is open read/write) Active-Active high availability (with conflict resolution) Heterogeneous platform and heterogeneous database support Potential zero downtime with custom application failover
Storage failures	Oracle Automatic Storage Management (MAA recommended)	Mirroring and online automatic rebalancing places redundant copies of the data in separate failure groups.
	Oracle Data Guard (MAA recommended)	Integrated client and application failover Fastest and simplest database replication Supports all data types Zero data loss by eliminating propagation delay Oracle Active Data Guard supports read-only services and DML on global temporary tables and sequences to off-load more work from the primary Database In-Memory support
	Recovery Manager with Fast Recovery Area, and Zero Data Loss Recovery Appliance (MAA recommended)	Fully managed database recovery and managed disk and tape backups
	Oracle GoldenGate	Flexible logical replication solution (target is open read/write) Active-active high availability (with conflict resolution) Heterogeneous platform and heterogeneous database support Potential zero downtime with custom application failover
Data corruption	Corruption Prevention, Detection, and Repair (MAA recommended) Database initialization settings such as DB_BLOCK_CHECKING, DB_BLOCK_CHECKSUM, and DB_LOST_WRITE_PROTECT	Different levels of data and redo block corruption prevention and detection at the database level
Data corruption	Oracle Data Guard (MAA recommended) Oracle Active Data Guard Automatic Block Repair DB_LOST_WRITE_PROTECT initialization parameter	In a Data Guard configuration with an Oracle Active Data Guard standby Physical block corruptions detected by Oracle at a primary database are automatically repaired using a good copy of the block retrieved from the standby, and vice versa The repair is transparent to the user and application, and data corruptions can definitely be isolated With MAA recommended initialization settings, Oracle Active Data Guard and Oracle Exadata Database Machine, achieve most comprehensive full stack corruption protection. With DB_LOST_WRITE_PROTECT enabled A lost write that occurred on the primary database is detected either by the physical standby database or during media recovery of the primary database, recovery is stopped to preserve the consistency of the database Failing over to the standby database using Data Guard will result in some data loss Data Guard Broker's PrimaryLostWrite property supports SHUTDOWN and CONTINUE, plus FAILOVER and FORCEFAILOVER options, when lost writes are detected on the primary database. See Oracle Data Guard Broker DB_LOST_WRITE_PROTECT initialization parameter provides lost write detection Shadow lost write protection detects a lost write before it can result in major data corruption. You can enable shadow lost write protection for a database, a tablespace, or a data file without requiring an Oracle Data Guard standby database. Note the impact on your workload may vary.
	Dbverify, Analyze, Data Recovery Advisor and Recovery Manager, Zero Data Loss Recovery Appliance, and ASM Scrub with Fast Recovery Area (MAA recommended)	These tools allow the administrator to run manual checks to help detect and potentially repair from various data corruptions. Dbverify and Analyze conduct physical block and logical intra-block checks. Analyze can conduct inter-object consistency checks. Data Recovery Advisor automatically detects data corruptions and recommends the best recovery plan. RMAN operations can Conduct both physical and inter-block logical checks Run online block-media recovery using flashback logs, backups, or the standby database to help recover from physical block corruptions Recovery Appliance Does periodic backup validation that helps ensure that your backups are valid Allows you to input your recovery window requirements, and alerts you when those SLAs cannot be met with your existing backups managed by Recovery Appliance ASM Scrub detects and attempts to repair physical and logical data corruptions with the ASM pair in normal and high redundancy disks groups.
Data corruption	Oracle Exadata Database Machine and Oracle Automatic Storage Management (MAA recommended) DIX + T10 DIF Extensions (MAA recommended where applicable)	If Oracle ASM detects a corruption and has a good mirror, ASM returns the good block and repairs the corruption during a subsequent write I/O. Exadata provides implicit HARD enabled checks to prevent data corruptions caused by bad or misdirected storage I/O. Exadata provides automatic HARD disk scrub and repair. Detects and fixes bad sectors. DIX +T10 DIF Extensions provides end to end data integrity for reads and writes through a checksum validation from a vendor's host adapter to the storage device
	Oracle GoldenGate	Flexible logical replication solution (target is open read/write). Logical replica can be used as a failover target if partner replica is corrupted. Active-active high availability (with conflict resolution) Heterogeneous platform and heterogeneous database support
Human errors	Oracle security features (MAA recommended)	Restrict access to prevent human errors
	Oracle Flashback Technology (MAA recommended)	Fine-grained error investigation of incorrect results Fine-grained and database-wide or pluggable database rewind and recovery capabilities
Delays or slow downs	Oracle Database and Oracle Enterprise Manager Oracle Data Guard (MAA recommended) and Enabling Continuous Service for Applications	Oracle Database automatically monitors for instance and database delays or cluster slow downs and attempts to remove blocking processes or instances to prevent prolonged delays or unnecessary node evictions. Oracle Enterprise Manager or a customized application heartbeat can be configured to detect application or response time slowdown and react to these SLA breaches. For example, you can configure the Enterprise Manager Beacon to monitor and detect application response times. Then, after a certain threshold expires, Enterprise Manager can call the Data Guard DBMS_DG.INITIATE_FS_FAILOVER PL/SQL procedure to initiate a failover. See the section about "Managing Fast-Start Failover" in Oracle Data Guard Broker. Database In-Memory support
File system data	Oracle Replication Technologies for Non-Database Files	Enables full stack failover that includes non-database files

Managing Unplanned Outages for MAA Reference Architectures and Multitenant Architectures

High availability solutions in each of the MAA service-level tiers for the MAA reference architectures and multitenant architectures are described in an easy to navigate matrix.

If you are managing many databases in DBaaS, we recommend using the MAA tiers and Oracle Multitenant as described in Oracle MAA Reference Architectures.

The following table identifies various unplanned outages that can impact a database in a multitenant architecture. It also identifies the Oracle high availability solution to address that outage that is available in each of the MAA reference architectures.

Table 4-2 Unplanned Outage Matrix for MAA Reference Architectures and Multitenant Architectures

Event	Solutions by MAA Architecture	Recovery Window (RTO)	Data Loss (RPO)
Instance Failure	BRONZE: Oracle Restart	Minutes if instance can restart	Zero
	SILVER: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware) or Oracle RAC One Node, and Enabling Continuous Service for Applications	Seconds with Oracle RAC, minutes with Oracle RAC One Node	Zero
	GOLD: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware and Enabling Continuous Service for Applications	Seconds	Zero
	PLATINUM: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware) and Enabling Continuous Service for Applications	Zero Application Outage	Zero
Permanent Node Failure (but storage available)	BRONZE: Restore and recover	Hours to Day	Zero
	SILVER: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware) and Enabling Continuous Service for Applications	Seconds	Zero
	SILVER: Oracle RAC One Node and Enabling Continuous Service for Applications	Minutes	Zero
	GOLD: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware) and Enabling Continuous Service for Applications	Seconds	Zero
	PLATINUM: Oracle RAC (see Oracle Real Application Clusters and Oracle Clusterware) and Enabling Continuous Service for Applications	Seconds	Zero
Storage Failure	ALL: Oracle Automatic Storage Management	Zero downtime	Zero
Data corruptions	BRONZE/SILVER: Basic protection Some corruptions require recover restore and recovery of pluggable database (PDB), entire multitenant container database (CDB) or non-container database (non-CDB)	Hour to Days	Since last backup if unrecoverable Zero or Near Zero with Recovery Appliance
	GOLD: Comprehensive corruption protection and Auto Block Repair with Oracle Active Data Guard	Zero with auto block repair Seconds to minutes if corruption due to lost writes and using Data Guard Fast Start failover.	Zero unless corruption due to lost writes
	PLATINUM: Comprehensive corruption protection and Auto Block Repair with Oracle Active Data Guard Oracle GoldenGate replica with custom application failover	Zero with auto block repair Zero with Oracle GoldenGate replica	Zero when using Active Data Guard Fast-Start Failover and Oracle GoldenGate
Human error	ALL: Logical failures resolved by flashback drop, flashback table, flashback transaction, flashback query flashback pluggable database, and undo.	Dependent on detection time but isolated to PDB and applications using those objects.	Dependent on logical failure
	All: Comprehensive logical failures impacting an entire database and PDB that requires RMAN point in time recovery (PDB) or flashback pluggable database	Dependent on detection time	Dependent on logical failure
Database unusable, system, site or storage failures, wide spread corruptions or disasters	BRONZE/SILVER: Restore and recover	Hours to Days	Since last database and archive backup Zero or near zero with Recovery Appliance
	GOLD: Active Data Guard Fast-Start Failover and Enabling Continuous Service for Applications	Seconds	Zero to Near Zero
	PLATINUM: Oracle GoldenGate replica with custom application failover	Zero	Zero when using Active Data Guard Fast-Start Failover and Oracle GoldenGate
Performance Degradation	ALL: Oracle Enterprise Manager for monitoring and detection, Database Resource Management for Resource Limits and ongoing Performance Tuning	No downtime but degraded service	Zero