Did you ever wonder why in the syslog (transaction SM21) some entries with the message "UNBUFFERED RV_BELEG" are shown:
The creation of this log had been introduced with note 1711468. The background had been to have a clue for investigation, when errors due to wrong modifications in number range user-exits (see note 1176705) occur.
Now in function module NUMBER_GET_NEXT an entry for the system log is prepared, in case a buffered number range is used, and the buffer is deactivated:
The other pre-reqisite for creation of the log is the definition of parameter no_syslog, which is in standard coding 'space', if you have not modified include LSNR3TOP:
Therefore if the number range object RV_BELEG is buffered, and in user-exit USEREXIT_NUMBER_RANGE of Include RV60AFZZ there is some logic present, to deactivate the buffering in specific cases (as described in note 363901) with a line:
no_buffer = 'X'.
then in the syslog mentioned entry "UNBUFFERED RV_BELEG" is created.
It could be that this is not intended, and the logging is not useful. In this case you should implement note 1913844.
Notes:
1711468 - NK: Syslog entry if IGNORE_BUFFER = 'X'
1176705 - BTC processes stop with the action "Direct Read NRIV"
363901 - Country-specific buffering RV_BELEG/number assignment in SD
1913844 - NK: Vorhandenes Intervall wird nicht gefunden
Knowledge Base Articles with general information on buffering in invoice creation:
1524347 Buffering of billing documents - invoice creation
1524325 Poor performance due to locks on table NRIV - Buffering of billing documents