Hi guys, anyone faced high latency on Oracle replication? I've tried increasing global batch size and placed the heavy tables in their own individual subscription. Table structure are the same between source and target. Any clues are much appreciated.

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#DataIntegration
#DataReplication

When I've seen this it's been an index issue where an index was missing.

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Will Hathcock
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Index is there. Seems that target is applying slower than the source.

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Original Message:
Sent: Thu March 03, 2022 09:38 AM
From: Will Hathcock
Subject: CDC high latency

When I've seen this it's been an index issue where an index was missing.

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Will Hathcock
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Hello, so as long as the index is a unique index or primary key, then a full scan of the target tables is avoided for insert and delete operations.

1) What is your definition of high latency?
2) Are your source and target servers' clocks synchronised?
3) The inference is that your target is an Oracle database. Please specify if this is not the case

The target database is often the bottleneck because you may have fewer connections in CDC updating the target database than there are on the source updating the source database.

Have you reviewed the performaning tuning document at https://www.ibm.com/docs/en/idr/11.4.0?topic=replication-performance-monitoring-tuning ?



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Robert Philo
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Original Message:
Sent: Mon March 07, 2022 11:53 PM
From: data icons
Subject: CDC high latency

Index is there. Seems that target is applying slower than the source.

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data icons
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Original Message:
Sent: Thu March 03, 2022 09:38 AM
From: Will Hathcock
Subject: CDC high latency

When I've seen this it's been an index issue where an index was missing.

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Will Hathcock

Hi Robert,

1) Latency reported in the MC. 
2) They are in sync
3) Both source and target are Oracle databases.

I have also reviewed the performance tuning documentation.

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data icons
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Original Message:
Sent: Tue March 08, 2022 12:50 AM
From: Robert Philo
Subject: CDC high latency

Hello, so as long as the index is a unique index or primary key, then a full scan of the target tables is avoided for insert and delete operations.

1) What is your definition of high latency?
2) Are your source and target servers' clocks synchronised?
3) The inference is that your target is an Oracle database. Please specify if this is not the case

The target database is often the bottleneck because you may have fewer connections in CDC updating the target database than there are on the source updating the source database.

Have you reviewed the performaning tuning document at https://www.ibm.com/docs/en/idr/11.4.0?topic=replication-performance-monitoring-tuning ?



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Robert Philo
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Original Message:
Sent: Mon March 07, 2022 11:53 PM
From: data icons
Subject: CDC high latency

Index is there. Seems that target is applying slower than the source.

------------------------------
data icons


Original Message:
Sent: Thu March 03, 2022 09:38 AM
From: Will Hathcock
Subject: CDC high latency

When I've seen this it's been an index issue where an index was missing.

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Will Hathcock

How many tps are you trying to replicate?

Generally, when I have had performance issues replicating data to Oracle destination tables using IDR CDC, it has been due to lack of indexes (already checked by you) and due to inefficient triggers on the destination table.  It does not mean that those are the only potential causes, but is good to check if there are unproperly developed triggers.

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Daniel Jose Lema Guanziroli
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