The data of a database is consistent at certain points in time (known as consistency points), i.e. all updating transactions are complete and the updates made by them have been committed to the database.
A consistency point is reached
on the normal end of a DBH session or a modifying utility routine
following a successful session restart
when the ALOG file is switched (e.g. due to overflow)
with the DAL command CHECKPOINT (only possible with independent DBH)
when the DBH handles certain events (e.g. deactivates a realm)
The ALOG file may be switched at the same time as a consistency point is reached. The consistency point (checkpoint) is then written. You can update the backup of a database up to this checkpoint using the BMEND utility routine and the completed ALOG file.
Leaving the consistency point when updating a database also signifies the start of the log interval for an empty ALOG file. The end of the log interval is set on reaching the consistency point. If the ALOG file is not switched now and updates continue to be written up to the next consistency point, interval of the ALOG file is increased by this time period. The end of the log interval is updated accordingly.