On Delete Cascade OracleSQL drop user username cascade User.Oracle business intelligence 11g system The entire system architecture is c.Data Guard.To steal liberally from Larry Carpenters book on Data Guard, Data Guard is a product of more than 1.We can trace the roots of todays Data Guard as far back as Oracle.Media recovery was used to apply archived redo logs to a remote standby database, but none of the automation that exists today was present in the product.Today we are going to look at the material on Data Guard and discuss the differences between Data Guard, Active Data Guard, and Golden Gate.We are going to look at what it takes to replicate from an on premise system to the cloud and from the cloud to an on premise system.On Update Cascade Oracle 11g Architecture ExplainedIt is important to know that you can also synchronize between two cloud instances but we will not cover this today.If we look at the books that cover this topic they include.Note that there are not any 1.Data Guard.This is primarily due to the technology not changing significantly between the 1.The key new release in 1.We will cover that more later.There are also books written on Active Data Guard and Golden Gate as well.If we take a step back and look at high availability, Data Guard is used to provide this functionality between systems.Oracle Data Guard provides the management, monitoring, and automation software to create and maintain one or more standby databases to protect Oracle data from failures, disasters, human error, and data corruptions while providing high availability for mission critical applications.Data Guard is included with Oracle Database Enterprise Edition and in the cloud the High Performance Edition.Oracle Active Data Guard is an option for Oracle Database Enterprise Edition and included in the Extreme Performance Edition in the cloud.Oracle Database Architecture' title='Oracle Database Architecture' />The home page for Data Guard provides links to white papers.There are also a significant number of blogs covering high availability and Data Guard.My recommendation would be to attend the Oracle Education Class or follow one of the two tutorials that cover Basic Data Guard Features and Active Data Guard Features.In both of these tutorials you learn how to use command line features to configure and setup an active standby relationship between two databases.E29597_01/server.1111/e17157/img/haovw022.gif' alt='On Update Cascade Oracle 11G Architecture' title='On Update Cascade Oracle 11G Architecture' />Larry Carpenter has done a really good job of detailing what is needed to setup and configure two database instances with these tutorials.The labs are a bit long 5.The key concepts around Data Guard are the mechanisms for replication and how logs are shipped between systems.The basic foundation of Data Guard centers around replication of changes.When an insert or update is made to a table, this change is captured by the log writer and replicated to the standby system.If the replication mechanism is physical replication the data blocks changed are copied to the standby system.If the replication mechanism is logical replication the sql command is copied to the standby system and executed.Note that the select or read statements are not recorded and copied, only the commands that write to storage or update information in the database.By capturing the changes and shipping them to the standby system we can keep the two systems in synchronization.Enabling and disabling Oracle constraints.UPDATE or DELETE command applied to a table with constraints enabled has the possibility of failing.CASCADE DROP.On Update Cascade Oracle 11g Architecture Poster' title='On Update Cascade Oracle 11g Architecture Poster' />If a client is trying to execute a select statement on the primary database and the primary fails or goes offline, the select statement can be redirected to the standby for the answer.This results in seconds of delay rather than minutes to hours as is done with disk replication or recovery from a backup.How the replication is communicated to the standby system is also configurable.You can configure a write and release mechanism or a wait for commit mechanism.With the write and release mechanism, the logs are copied to the standby system and the primary system continues operation.With the wait for commit mechanism the primary stalls until the standby system commits the updates.Significant improvements were made in 1.LNS and the redo apply service RNS.The LNS has the ability to delay the shipping of the logs in the asynchronous update mode and can compress the logs.The RNS knows how the LNS is configured and can get decompress the logs and apply them as was done before.This delay allows for the LNS to look for network congestion and ship the logs when the network is not so overloaded.The compression allows the packet size to be smaller to reduce contention on the network and make the replication more efficient.It is important to note that you can have a single LNS writing to multiple RNS targets to allow for replication not in a one to one configuration but in a one to many configuration.It is also important to note that this technology is different from table cloning or data masking and redaction that we talked about earlier.The assumption is that there is a master copy of the data on the target system and we only ship changes between the systems when an update occurs on the primary.The key difference between Data Guard and Active Data Guard is the state of the target database.With Data Guard, the database can not have any active sessions other than the RNS agent.You can not open the database for read only to do backups or analytics.Having an active sessions blocks the RNS agent from committing the changes into the database.Active Data Guard solves this problem.The RNS agent understands that there are active connections and can communicate changes to the active sessions if they are reading data from updated areas.A typical SQL connection uses buffering to minimize reads from the disk.Reads are done from an in memory buffer to speed up requests.The problem with reading data on a standby system is invalidation of these buffers.With Data Guard, there is no mechanism to invalidate buffers of sessions on other connections. Battlefield 2 1 41 Cd Crack Generals more. D Home Design Software Free Download For Windows Xp .With Active Data Guard, these mechanisms exist and updates are not only written to the disk but the cache for the other connections are updated.Golden Gate is a more generic case of Active Data Guard.One of the limitations of Data Guard is that you must have the same chip set, operating system, and database version for replication.Translations are not done when changes are shipped from primary to standby.You cant for example replicate from a Sparc Server to an X8.Oracle database.One uses little endian while the other uses big endian to store the bits on disk.Physical replication between these two systems would require a byte translation of every change.Data Guard does not support this but Golden Gate does.Golden Gate allows you to no only ship changes from one database instance to a different chip architecture but a different chip architecture on a different operating system running a different database.Golden Gate was originally crated to replicate between database engines so that you could collect data with SQL Server and replicate the data to an Oracle database or My.SQL database so that you could do analytics on a different database engine than your data collection engine.With Golden Gate there is a concept similar to the LNS and RNS but the agents are more intelligent and promote the data type to a master view that can be translated into the target type.When we define an integer it might mean 3.Golden Gate is configured to lead fill from 3.To replicate between two systems we basically need an open port from the primary system and the standby system to ship the logs.We also need a landing area to drop the change logs so that the RNS can pick up the changes and apply them.This prohibits Amazon RDS from enabling Data Guard, Active Data Guard, or Golden Gate since you do not have file system access.To run Data Guard in Amazon or Azure you need to deploy the Oracle database on a compute or Iaa.S instance and purchase the perpetual license with all of the options associated with the configuration.The beautiful thing about Data Guard is that it uses the standard port 1.There are special commands developed to configure and setup Data Guard that bridge between the two systems.As data is transmitted it is done over port 1.RNS agent.
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