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Comparison and coexistence of Integrated Synchronization and Change Data Capture for incremental updates

By Ute Baumbach posted Wed April 01, 2020 10:44 AM

  
In the first blog entry of the series of blog entry about Integrated Synchronization an overview about the new data synchronization technology was provided.
See here: Integrated Synchronization overview, architecture and setup
This blog entry focuses on how incremental update with Integrated Synchronization compares to incremental update with IBM Change Data Capture (CDC) of InfoSphere® Data Replication for z/OS®.  Additionally this blog entry describes how both incremental update techniques can coexist in environments with multiple accelerators or Db2 subsystems.

Comparison of Integrated Synchronization versus CDC for incremental updates

The following table compares both techniques for incremental updates from a functional, setup, maintenance, performance and resource consumption perspective. The comparison is based on Db2 Analytics Accelerator V7.5 and outlines the differences.

 

 

Integrated Synchronization

CDC

Installation and setup

Streamlined and optimized design tailored specifically for Db2 z/OS -> Db2 Analytics Accelerator replication, resulting in less CPU consumption and better throughput

General purpose replication technique supporting multiple sources and targets

 

New log data provider component integrated into Db2 for z/OS for capturing table updates from the Db2 for z/OS log. Initial installation by applying a Db2 for z/OS PTF. New log data processor component integrated into Db2 Analytics Accelerator.

CDC capture agent installation and setup required for capturing table updates from the Db2 for z/OS log.

CDC apply components are included in Db2 Analytics Accelerator.

 

Supported with Db2 12 only

Minimum prerequisite: Function level V12R1M500 with APAR PH06628 (PTF UI63356)

Supported with Db2 11 and Db2 12

 

Log data provider maintained by applying Db2 PTFs

CDC capture agent maintained by applying CDC PTFs

 

Db2 DDF secure port and AT-TLS network encryption setup required

No encryption required, but optional configuration of encryption of data-in-motion possible

 

Optional support for RACF PassTickets for Db2 z/OS authentication from accelerator via Db2 DDF as an alternative to user ID/password authentication method

Db2 for z/OS authentication from accelerator via Db2 DDF with user ID/password only.

 

High-Availability setup for log data provider component in data sharing environments on the roadmap

High-Availability setup of the CDC capture agent in data sharing environments supported

CPU usage and latency

50% less CPU consumption on z/OS compared to CDC.

Higher CPU consumption on z/OS

 

This workload to capture changes from the Db2 log is fully zIIP enabled

Full CDC Capture Agent workload to capture changes from Db2 log runs on GP processors (not zIIP enabled)

 

Significant reduction in replication latency.

Latency < 10 seconds

Latency around 30 seconds, can be more or less depending on workload. Higher with significant “True HTAP” workload.

 

“True HTAP” query scalability significantly improved. Usage of WAITFORDATA protocol for concurrent queries has practically no impact on throughput and latency

Usage of WAITFORDATA protocol for queries may impact replication throughput and latency

Functional differences

Replication of Db2 archive tables (Transparent Archiving) supported

No support of replication of Db2 archive tables (Transparent Archiving), because of a CDC limitation

 

On the roadmap:

  • Option to change the IP address of the Log Data Provider on the accelerator
  • Automatically disable query acceleration when table no longer replicated
  • Replication of schema changes (First stage: ALTER TABLE xxx ADD COLUMN)

Currently there are no plans to make any additional features available for CDC usage (such as the ones that are on the roadmap for Integrated Synchronization).

 

Coexistence of Integrated Synchronization and CDC

Mixed CDC and Integrated Synchronization environments that perform incremental updates to one or more accelerators are supported. For each Db2 for z/OS connection to an accelerator (“pairing”) you can decide whether to enable incremental updates based on Integrated Synchronization or CDC. For example, for Db2 subsystems still on Db2 for z/OS V11 you can enable incremental updates using CDC, while for Db2 on z/OS V12 subsystems that have the prerequisites installed, it is recommended that you enable incremental updates using Integrated Synchronization.

  • One accelerator supports both incremental update techniques
  • From the same Db2 subsystem, both the same or different data can be replicated to one accelerator with CDC and to another one with Integrated Synchronization. This configuration might be used in a coexistence scenario where one accelerator is still on V5 and the other one on V7.

The following figure illustrates an environment in which two different Db2 subsystems replicate data to a single accelerator. The Db2 subsystem on LPAR1 replicates to the accelerator using Integrated Synchronization and Db2 subsystem on LPAR2 replicates to the accelerator using CDC. Examples of such an environment could be the following:

  • The Db2 subsystem on LPAR1 is a test system with Integrated Synchronization already implemented for test purposes. The Db2 subsystem on LPAR2 is a production system still using CDC for replication. After a successful test of Integrated Synchronization, the replication setup on LPAR2 will be migrated from CDC to Integrated Synchronization
  • The Db2 subsystem on LPAR1 is already running Db2 for z/OS V12 with all prerequisites in place and can therefore use Integrated Synchronization to replicate data to the accelerator. The Db2 subsystem on LPAR2 is still running Db2 for z/OS V11 and therefore uses CDC to replicate data to the accelerator.

  Coex1.png

The following figure illustrates an environment in which one Db2 subsystem replicates data to two accelerators. The Db2 subsystem replicates data to Accelerator 1 using Integrated Synchronization and to Accelerator 2 using CDC. An example for such an environment would be a coexistence environment of a V5 accelerator and a V7 accelerator during a migration phase from version 5 to version 7. Both versions are set up in coexistence mode until migration has completed and the V5 accelerator can be removed. In this example the Db2 subsystem replicates to a V5 accelerator using CDC and to a V7 accelerator using Integrated Synchronization.

Coex2.png



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