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Re: URGENT: Hot StandBy database feature

From: William Beilstein <>
Date: Wed, 07 Jun 2000 15:59:17 -0400
Message-Id: <>

The following is from Oracle Technet

Rdb7: Hot Standby Option for Disaster Tolerant Systems=20 Oracle Rdb Release 7.0 and Oracle CODASYL DBMS Version 7.0 introduce new = Hot Standby software that physically duplicates a database as a means of = providing disaster tolerance. By implementing the Hot Standby option, = businesses with mission-critical requirements can prevent the catastrophic = loss of data and data processing capability. Failure detection and = failover can be achieved with minimal interruption to database users and = application processing.=20

The Hot Standby software prevents an Oracle Rdb database or Oracle CODASYL = DBMS database from becoming a single point of failure by physically = duplicating a master database at a geographically-remote standby site = across a wide area network. In the event of a node or cluster failure, the = "hot standby" database becomes the master database and takes over = application processing.=20

Automated AIJ Backup and Roll-Forward Operations=20

The standby database is created from a backup copy of the master database. = Once started, the replication operation rolls forward the group commit = operations to the standby database. As database modifications are applied = to the after-image journal (AIJ) for the master database, the Hot Standby = option automatically applies the modification over a network connection to = the after-image journal for the standby database.=20

Automatic Database Synchronization=20

The Hot Standby option automatically performs coordinated database = synchronization and verification with high performance and minimal impact = on system resources:=20

Starting the replication services is the only manual intervention = required.=20
"Replication Governor", an optional component, coordinates the database = replication operation, effectively ensuring synchronization between the = master and standby databases.=20
The degree to which the master database and standby database stay = synchronized can be determined by the DBA. Consistency levels range from a = fully asynchronous "fire-and-forget" model to a synchronous "transaction = commit" level in which data modifications are made to both databases.=20 Four server daemons, two on the master database and two on the standby = database, are deployed to implement client/server relationships that are = necessary to provide database replication and verification services. The = four-process model means that the master database cluster resource = requirements and performance impact are minimal, while all available = resources on the replicated system are fully utilized.=20 No specific hardware is required to use the Hot Standby option.=20 No changes to application code are required.=20 Replication Commands=20

To start the replication operation, a Replicate command can be entered = using either the Rdb Management utility (RMU) or the DBMS Database = Operator (DBO) utility, as appropriate. These utilities provide syntax and = semantics for the following Replicate commands:=20

Command Description=20
Replicate After_Journal Start Initiates replication operations on the = master node or the standby node=20
Replicate After_Journal Stop Terminates replication operations for the = database=20
Replicate After_Journal Reopen_Log Allows the opening of a new replication = log file=20


The Hot Standby option is completely compatible with the standard Oracle = Rdb and CODASYL DBMS database components. All database DDL and DML = functionality is fully supported.=20

Hot Standby allows users to choose from among OpenVMS VAX, OpenVMS Alpha, = or Digital UNIX operating system platforms for both the master and the = standby systems, mixing and matching as follows:=20

For Oracle CODASYL DBMS databases, the master and standby databases can be = implemented on systems running OpenVMS VAX, OpenVMS Alpha, or both.=20 For Oracle Rdb databases, the master and standby databases can be = implemented on systems running OpenVMS VAX, OpenVMS Alpha, Digital UNIX, = or a combination of these operating systems.=20 For example, a master database running on an OpenVMS Alpha system can be = replicated on a standby database running on a Digital UNIX system. The = only requirement is that the network connection is common to both = operating system platforms. The Hot Standby option uses the following = network transport protocols:=20

DECnet for OpenVMS=20
Failure Handling=20

The standby cluster configuration is separate and distinct from the master = database configuration. System failure of either the master or standby = database is completely isolated from the other. Neither database is = effected by the failure of the other.=20

Applications must be manually failed over to the hot-standby database if a = failure occurs. There is=20

no automatic failover support. However, the Hot Standby software automatica= lly provides failover detection and notification for varying levels of = failures: network, cluster, node, disk, server process, application = process, database monitor, and other resources (such as process quotas, = disk quotas, or disk space exhaustion).=20

For More Information=20

Contact your Oracle Sales Representative, your Oracle Sales Office, or = call 1-800-ORACLE1. Outside of the United States please call 415-506-5701. = You may also send electronic mail requests to or = call the Oracle Rdb Hotline: 603-881-0956.=20 =20

>>> Balasubramanian M <> 06/07/00 03:18PM >>>

Dear all,

I did not get any response for my earlier mail which is given below. How standby database works the sense when production database fails how the standby take over whether automatic or manual switch over. How the transaction is written to both the databases ?=20 In case production database fails , whether there will be any loss of data.=20

I hope some one on the list can help me.

Thanks & Regards,

On Tue, 6 Jun 2000, Balasubramanian M wrote:


> Dear all,

> Our client considering the option of hot standby database feature.
> Can any one explain, what is hot standby database ? What are the=20
> advantages and disadvantages of using it ? In what way it differs =
> Replication ?=20

> Is there any thread, white paper or URL available on this subject ?=20
> We have to take quick decision on this to inform the client.=20

> I would really appreciate if you can provide info. on this.

> Thanks & regards,
> bala


Author: Balasubramanian M

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