Ruleset parallel execution issue

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Hi,

I got a weird issue when running a ruleset with parallel execution enabled, and want to seek for any insights.

I have a Groovy rule to copy/calc data across years(say 10 years) using datagrid for data submission. Originally, running 10 years all together in one run is all good except for the running time is bit slow. The years have no dependencies, so I consider to run the rule with runtime prompt for year, and repeat the rule in a ruleset for 10 times with different year prompts as default and enable parallel execution to speed up the timing.