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ORACLE DATA GUARD VS DELL SHAREPLEX

oracle-data-guard-vs-dell-shareplex

There are many data replication solutions for your Oracle database, in this case we will compare the Oracle SharePlex and Oracle Data Guard database replication technologies by analyzing the general differences between them and the different usage scenarios.

ORACLE DATA GUARD

 MAJOR CHARACTERISTICS

  • Oracle Data Guard is one of Oracle’s database replication solutions.
  • Oracle-Oracle Replication.
  • Free with Oracle Enterprise License.
    • It is mandatory to have licensed the DB itself.
  • Oracle Data Guard provides High Availability, Disaster Recovery and Data Protection.
  • From a primary DB, it is possible to have up to 30 DB standby.
    • The standby DB can be on LAN or WAN.
  • Oracle Data Guard Broker is the Data Guard management framework for managing, maintaining, and monitoring Data Guard configurations via Oracle Enterprise Manager or Data Guard command-line interface (DGMGRL).

 

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TYPES OF DB STANDBY

  • Physical Standby Database.
    • It provides an identical copy of the primary DB, where the structure of the DB at disk level is identical at block level. The DB schemes, including indexes, are identical.
    • Stays in sync with the primary database using Redo Apply technology.
    • We can open the DB in read-only mode, although we’ll have to stop the replication.
  • If we license Active Data Guard, a physical standby database can receive and apply redo when it is open in read-only mode.oracle-vs-shareplex-2
      • While replication is active (via redo apply), the standby DB will not be open.
      • If we want to open the DB for reporting it is necessary to stop the redo apply.
      • We can only have replication and reporting active simultaneously with Active Data Guard (Real-Time query + Read Only), which must be licensed.
  • Logical Standby Database.
    • It contains the same logical information as the primary database, where the physical organization and structure of the data can be different.
    • Stays in sync with the primary database using SQL Apply technology.
    • SQL Apply transforms the received redo information into SQL sentences that are applied in the standby DB.
    • The DB can be open in Read/Write mode, although the tables managed with Data Guard must be in read only.
    • There is no Active Data Guard for logical standby DB -> no point, because the DB is already open by default.oracle-vs-shareplex-3

 

PROTECTION METHODS

  • Maximum Availability
    • Maximum guarantee of data protection without compromising availability
    • Transactions are committed when one of the two options (configurable) is met in at least one of the DB standby:
    • have been received in memory, or
    • have been written in the SRL (standby redo log)
    • If it cannot send the redo stream, it behaves as if it were in Maximum Performance mode, to preserve availability until the redo is retrieved
  • Maximum Performance
    • Maximum data protection guarantees without compromising performance
    • Transactions are commented on when they have been written in the online redo log
    • The redo is also written to standby DB but is done asynchronously
  • Maximum Protection
    • There will be NO data loss in case the primary DB falls
    • Transactions are committed when transactions are written both in the online redo log and in at least one SRL (standby redo log)
    • If you cannot send the redo stream, the primary DB stops

 

DELL SHAREPLEX

INTRODUCTION

  • SharePlex® is an asynchronous replication solution between Oracle DB and other heterogeneous DBs as a target
  • Real-time replication
  • Replication for Oracle Enterprise and Oracle Standard databases
  • Flexibility to support different configurations and easy administration
  • SharePlex includes all the tools needed to manage the replicated environment: Data Comparison, Synchronization and Monitoring at no additional cost
  • Simplifies replication by offering the best performance and full data integrity security
  • Supports horizontal (replicate only certain rows), vertical (replicate only certain columns) and data transformation segmentation
  • Bidirectional or unidirectional replication architecture.
  • oracle-vs-shareplex-4

 

Supported scenarios

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OVERALL DIFFERENCES

  • ODG only allows replication between Oracle-Oracle, DSP allows replication between Oracle-Heterogeneous Managers, including Oracle, SQL Server, Postgre…
  • ODG only allows to replicate Oracle Enterprise DB; DSP allows to replicate both Enterprise and Standard
  • Configuration and Management of replication is more complicated in ODG than DSP
  • Slower data transmission in ODG than in DSP
  • More complex failback management in ODG than in DSP
  • Much higher bandwidth usage and network latencies in ODG because it sends all the redo log to the standby DB, while in DSP only the data changes are sent
  • The target DB is fully open in DSP, while in ODG, depending on the standby DB type, it will be mounted (physical standby), open as read-only (physical standby without simultaneous replication or physical standby + Active Data Guard) or open in read/write mode except for the replicated tables which will be in read-only (logical standby)
  • Limited platform/operating system independence in ODG, while in DSP it is completely platform/operating system agnostic
  • Independence of the limited DB version in ODG (only with logical standby), while in DSP it is totally agnostic of the DB version
  • Creation of new objects (views, indexes) in limited standby in ODG (only with logical standby), while in DSP it is totally valid
  • Limited flexibility of objects to be replicated in ODG (in physical standby it is necessary to replicate the whole DB), while DSP allows to replicate only certain schemes/tables
  • In ODG (if Real-time apply, which also includes Active Data Guard, is not active) you can enter a delay in replication, while in DSP it is not possible
  • The use scenarios that ODG can cover are limited, while DSP can cover the various possible use scenarios in a replication
  • DSP enables two-way replication
  • DSP can be used as an ETL, performing some data transformation when replicating
  • In ODG and DSP, you can stop replication to test with the target environment, while in Oracle Active Data Guard you cannot

 

 

DIFFERENCES – USE SCENARIOS

The specific differences between ODG and DSP for the following usage scenarios will be discussed below:

 

  • High Availability and Disaster Recovery
  • Migrations, patches and upgrades
  • Reporting, Archiving, Data Warehousing
  • Data distribution, distributed processing
  • Cascading
  • Centralized Reporting
  • Change Tracking
  • Load balancing/Active-Active
  • Data integration

DIFFERENCES – USE SCENARIOS: HIGH AVAILABILITY AND DISASTER RECOVERY

  • Both ODG and DSP allow for a high availability environment or Disaster Recovery, to ensure 24×7 availability
    • At ODG we would prefer to use physical standby
  • ODG configured in Maximum Protection mode is the only one that guarantees that no data will be lost under any circumstances in the target environment. Both DSP and ODG in their Maximum Availability and Maximum Performance modes cannot guarantee that no data will be lost in the event of a possible incident
    • Please note that Maximum Protection mode is a synchronous replication, which can affect performance, and that in case of loss of communication, the primary DB is automatically stopped
  • With ODG physical standby, it is not possible to combine standby for HA/DR and Reporting, while in DSP it is possible to do both
    • With Oracle Active Data Guard or ODG logical standby it is possible to combine
  • DSP is faster at replicating information because of the smaller volume of data to be transferred, since ODG must move the entire redo log
  • DSP allows for different platform/operating system/Oracle versions, while ODG does not
  • DSP allows the HA/DR destination database to be Oracle Standard

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DIFFERENCES – USE SCENARIOS: MIGRATIONS, PATCHES AND UPGRADES

  • ODG would only allow to migrate or patch DB Oracle Enterprise, while with DSP we could migrate/patch both Oracle Enterprise and Standard
  • We could NOT use ODG for migrations involving platform/operating system changes, because ODG does not allow replication between different platforms/SOs
  • For DB version migrations, ODG logical standby allows different Oracle versions in source and target
  • ODG physical standby forces the Oracle version to be the same, so you can only use the target environment to apply one-off patches, PSUs (patch set updates) and CPUs (critical patch updates) in rolling mode, and not to migrate Oracle versions
  • DSP allows maximum flexibility for DB, platform and operating system version migrations, without any restrictions. Also, there are no restrictions for one-offs, patches, etc…
  • Both ODG and DSP allow you to use the target environment for application testing
  • DSP allows for two-way replication, so the turnaround is easier in DSP
  • DSP minimizes redo latency by not having to send the entire redo
  • DSP allows migration to Oracle Standard

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DIFFERENCES – USE SCENARIOS: REPORTING

  • Limitations of ODG in its different editions for reporting
    • With ODG physical standby:
      • you cannot simultaneously have the DB open in read-only mode with the redo con application, so if you want to use it for reporting, it would be with non-real data
      • You must replicate the entire database
      • Cannot create indexes or other target objects to improve performance
      • Replication from different sources is not allowed to have a centralized reporting instance
    • With Active Data Guard:
      • you can simultaneously have the DB open in read-only mode with the redo application
      • The DB is in read-only, so you can’t write about it
      • You must replicate the entire database
      • Cannot create indexes or other target objects to improve performance
      • Replication from different sources is not allowed to have a centralized reporting instance
    • With ODG logical standby:
      • The DB can be open in read/write mode, but the tables managed by ODG must be in read-only mode
      • You can replicate the DB partially (certain tables, schemes…)
      • You can create indexes or other target objects to improve performance
      • Replication from different sources is not allowed to have a centralized reporting instance
    • DSP lacks the limitations of ODG:
      • DSP allows to have the target DB open in read/write mode for all tables
      • DSP allows maximum flexibility of objects to be replicated (tables, schemas…)
      • DSP allows to create indexes or other objects on target to improve performance
      • DSP allows replication from different sources to have a centralized reporting instance
      • DSP allows the versions of DB/platform/so involved in the mirror to differ
      • DSP minimizes redo latency by not having to send the entire redo
      • DSP allows the reporting database to be Oracle Standardoracle-vs-shareplex-mini3

 

DIFFERENCES – USE SCENARIOS: DATA DISTRIBUTION, DISTRIBUTED PROCESSING

  • Both ODG and DSP allow data to be distributed from one source to several destinations:
    • Oracle Data Guard:
      • Allows up to 30 standby databases
      • Review HA/DR and Reporting use scenarios for detail on allowable use cases
    • Dell SharePlex:
      • Allows for N destinations
      • Review HA/DR and Reporting use scenarios for detail on allowable use cases
    • oracle-vs-shareplex-mini4

 

DIFFERENCES – USE SCENARIOS: CASCADING

  • With ODG only available for Oracle Enterprise version. With DSP, it could be used with both Oracle Enterprise and Oracle Standard
  • Both ODG and DSP allow data to be distributed from one source to several destinations using intermediate environments:
    • Oracle Data Guard:
      • It can be done both with physical standby and with logical standby using that standby as a source for another physical or logical standby destination. Data is stored in intermediate standby, and can assume a primary role at any time
      • You can use Data Guard Far Sync Configuration, where you define intermediate systems that only send data, without storing it, so they can never assume a primary role
      • Review HA/DR and Reporting usage scenarios for more details on usage
    • Dell SharePlex:
      • Allows maximum flexibility to configure a cascade replication, either by storing data on the intermediate systems, or without storing it. In the case of non-storage, no DB would be required on the intermediate systems
      • Review HA/DR and Reporting usage scenarios for more details on usage.oracle-vs-shareplex-mini5

 

DIFFERENCES – USE SCENARIOS: ALL OTHER SCENARIOS

  • The scenarios included in this section are as follows:
    • Centralized Reporting
    • Change Trackin
    • Active-Active Replication/Load Balancing
    • Data integration
  • ODG does not support these usage scenarios
    • Oracle has Oracle Golden Gate to cover these scenarios
  • DSP covers all scenarios.oracle-vs-shareplex-mini6
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    oracle-vs-shareplex-mini9

 

WOULD IT MAKE SENSE TO COMBINE ODG AND DSP?

  • It is possible to combine ODG and DSP to cover different needs
  • Examples:
    • Ex1: I have ODG configured for DR and DSP for reporting
    • Ex2: I have ODG configured for DR and DSP for data centralization in a DWH
    • Ex3: I have ODG configured for DR and DSP to distribute localized data
    • Ex4: I have ODG configured for DR and DSP for bi-directional replication
    • Ex5: Using ODG for replication on LAN and DSP for replication on WAN to optimize bandwidth

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