Couple things
- the syntax exec('commit') may not be supported in future revisions per a response I got from development in a previous OSS message, so I would be careful how much you are using this.
- I would differentiate the discussion between commit (for which all the work in a SP is done at the procedure completion point) and the merge process, these are two separate topics. If you are concerned with the commit happening on too much data, consider splitting it up logically into separate runs. If you find you have issues with the merge process, first ensure your table is partitioned appropriately, then look into the suggestions given by PK. I'm with Lars here, my findings tell me that if the tables are partitioned appropriately, auto merge works fine.
Happy HANA,
Justin