Note: I wrote this answer before I realized this was on Azure SQL DB (David's answer seems to indicate this is legit buggy behavior in Azure).
Leaving here as the OP was also looking for an explanation about what that error meant, and maybe it will be helpful for others in an on-prem setup with this error.
Your transaction log is full. Looking at the screenshot you shared, it's only 59 MB. Which is pretty small. One would think it would just keep growing to accommodate more transactions. But it can't for some reason.
SQL Server wants to start re-using the log file. But you've got that pesky
OLDEST_PAGE thing happening. This means that there are modified date pages in memory that haven't been persisted to the data file on disk, and thus SQL Server can't start re-using the part of the transaction log that documents those potentially-unpersisted transactions.
A temporary fix would be to run the
CHECKPOINT command manually on the server, to try and force those buffered pages to be flushed to disk. You may have to run the command more than once, but this will allow that transaction log file to start being reused.
The bigger problem is with your transaction log. You should run this query:
select max_size, growth from sys.master_files where [name] = 'YourLogFileName';
max_size to see if there is an explicit maximum preventing your log file from growing
If this is the case, set
max_size to a larger number to accommodate your actual transactional load. The number for this will depend on your usual number of transactions, and what recovery model you're using.
growth to see if autogrowth has been disabled (growth = 0)
If it is disabled, you could enable it.
If you can't do that, and you're in FULL recovery model, you could schedule more frequent log backups.
If you can't do that, and you're in SIMPLE recovery model, you'll need to increase the size of the log file manually until it's large enough to handle the transactions you have between automatic or indirect checkpoints.
It's possible, maybe, that the disk of your Azure storage is full and that's what is preventing the file from growing (although I'd expect different error messages).