I am experiencing CDC performance issues in the form of low Apply Throughput when applying to target.
I am using the Qlik Replicate solution on RedHat Linux with an external Oracle Database as source with ASM and target being a MSSQL Database.
My goal is to have a complete image of the Oracle Database at all times within a couple of minutes of delay. Which would require a throughput of no less than 2.000 kb/s.
However, I am experiencing serious CDC performance issues with an average Apply Throughput of < 400 kb/s, with Incoming Changes waiting to be applied piling up causing an ever increase in delay.
We have an idea that our issue is caused by the unusual database with CLOBS over 300 GB. However, our Full Load is showing throughputs 100x better than our CDC, which leads me to believe that there might be an obvious configuration that I am overlooking.
Some notes:
- Full Load is able to finish in less than 20 hours with throughput reaching over 40.000 kb/s.
- If using a null target - instead of MSSQL - I get satisfying CDC performance.
- We have a few tables with columns containing CLOBS of 300GB in size.
- Tried several settings such as tuning Replicate Lob Columns
- Used the Perl scripts (link above) to locate transfer issues, which all points to be a issue when applying to target.
- Splitting the replication into 3 different tasks. (1) for creating a log stream (2) replicating without CLOBS using the log stream as source (3) replicating the CLOBS also using the stream as source.
