Thank you for your hints.

I also think now that it is not good to shrink the transcation log to 1MB.

Although the recovery mode is set to simple (so only the last transactions is stored in the transaction log),

the growth of the transaction log is an expensive operation.

But, why should the transaction log size set to 10% of the database size?

Has someone experiences which is a good value in simple recovery mode?

Regards,