Hi Kazuki,
If your question is regarding increasing parallel jobs
1. For Initial load then you need to increase the number of Initial load jobs to the available extent.
2. For Replication then you need to decrease the number of initial load jobs and increase the value of No. of Data transfer jobs.
If not the above scenario then please ignore the suggestion.
How to find the number of available jobs:
In the Configuration and Monitoring Dashboard (t-code ltr), select your configuration, click on it, select Jobs and connections tab as shown above.
You will change by clicking on Edit and go to Settings tab.
Regards
Raj