Greetings!

1) your write "embedded" mode, but your URL shows File access (not
Memory)
2) you don't state the H2 version you are using
3) maybe provide a simplified, self containing test for people to look
at the details

In general, large DML on indexed columns/tables can lead to "write
amplification". I filed a similar issue 2 years back.
The received advice was:

1) remove indexes, update, create indexes (effective, but not nice)
2) update smaller portions (is this what you mean with "split" mode?)

Best regards
Andreas



On Wed, 2023-07-19 at 07:24 -0700, Andrii Odnoviunenko wrote:
> Hello, 
> 
> We face the following  performance   issue of the H2 Database V2 in
> the embedded mode is not good 
>  (UPDATE statement for 1 column in a table with 1 Million dataset
> with a unique index column ) takes about 40 seconds
> 
> jdbc:h2:file:XXXXXX:CACHE_SIZE=6000000;QUERY_CACHE_SIZE=16;
> 
> also "merge into" statements with a join between 2 indexed columns
> are comparably slow. 
> In general the performance is times worse than in a test with Oracle
> database
> 
> various settings have been tried (increasing cache size helped a bit,
> but not much
> I have also tried the "split" mode and changing page size to other
> values (there have ben only marginally small performance gains)
> 
> Please advice what the reason can be? Which other settings may cause
> this performance issue?
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