One task for every redo log thread

[Willie Zhu]

Hi team, 

   We are running debezium for our RAC oracle,  it take several seconds to fetch result from logminer, we want to improve that.  As we have two redo log threads, can we support to run seperate task for every redo log thread?

[Chris Cranford]

Hi Willie -

So my understanding of Oracle RAC is a bit limited, but my understanding is that even though each node has its own redo log thread for writing to its own logs, SCN assignment to a change vector is still global across all instances, correct?  In other words, if I wanted to get all changes that happened between SCN 12345 and 12350, then that range may only pertain to a single node or multiple nodes depending on what change vectors were captured during that range.  More to the point, I would expect I could get the following:

Thread 1 - SCN 12345
Thread 2 - SCN 12346
Thread 1 - SCN 12347
Thread 1 - SCN 12348
Thread 2 - SCN 12349
Thread 1 - SCN 12350

Lets assume that LogMiner allows us to do this, could a transaction span across multiple nodes?  What about multiple nodes modifying the same table; i.e. we'd need to chronologically sort the events now across each task, right?

On 10/8/21 04:08, Willie Zhu wrote:

Hi team, 

   We are running debezium for our RAC oracle,  it take several seconds to fetch result from logminer, we want to improve that.  As we have two redo log threads, can we support to run seperate task for every redo log thread? --
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