Hi,
as master database does not have separate data and log, you can first try to truncate the transaction log:
dump tran master with truncate_only
afterwards you should run a full database dump !!!
If this does not work you can increase the master database. For this free space on the master device is required. You can check this with:
sp_helpdevice master
If you don't have any free space on the master device, you have to resize it first (here by 50 MB):
disk resize name = 'master', size = '50M'
Now you can increase master database (here by 20MB):
alter database master on master = 20
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Segments are used to control the placement of objects. System segment contains system tables (like sysusages), default contains data, and log contains the transaction log. By increasing the database the segment will also be increased.
Best regards,
Juergen