MaxDB (SAP) doesn't support parallel backups on same instance and there can be only one backup operation active on database at the same time.
For same reason Data Protector also doesn't support parallel backups and it is documented:
SAP MaxDB does not support parallel backups of the same instance and there can be only one backup operation active on database at the same time. Data Protector also does not support parallel backups of database and logs.
Currently running backups in parallel will cause backup failure because of bsi_* files that have same names and that are needed for MaxDB database manager are deleted/overwritten. This means that if a Log backup starts while online backup of a MaxDB system is running, then this online backup will fail.
Idea is created to implement some locking mechanism that will detect if MaxDB backup is already running and if yes, it will pause another backup until first one finish so that both backups are successful or something similar to avoid the first online backup fails.