InnoDB error: exceeded log capacity...but only during import I see this error in mysql.log:

InnoDb error: the age of last checkpoint is...which exceeds the log group capacity etc..


I think I understand it, but the fact is that it's happening only during a night operation at minimum load,  consisting in a 100MB db import.

I import the result of mysqldump --opt, with the purpose of duplicating a db for testing.

The error suggests an increase in the log file x 10 times.

Considering that in no way I'm reaching this limit during normal daily time, I wonder if there is another way of dealing with the problem, rather than changing the log file size and restarting mysql...

The speed of the import operation is not important. 

Mysql v5.1.69
You are probably trying to import very large rows. The 5 MB default log file size (10MB in total for the log) may be too small in many cases. The default for 5.6 is 50MB (100Mb in total), which is probably a more sane default in most cases.

If you do not have much load, the only problem of augmenting the log is having to handle a larger set of files, nothing else should change (this is not true in heavy-write environments). it will also make the load process much faster, assuming you have enough memory size for the buffer pool. You may want to change the innodb_log_buffer_size if you are loading lots of large rows.

Check a tutorial on how to change the transaction log size in MySQL 5.1.