why archive vary in size

Hi, We are doing archive level 0 to disk daily. We noticed that the size of the file goes up and down greatly, more than the activities of the database itself. We have asked Informix, they dont have explanation. One guy said that it's because of logical logs that being backed up. So sometimes that logs are big and sometime they are small. But the Informix consultant said that archive level 0 does not save the logs in the level-0 only the log id. What's really going on??? We are using Informix 5.05 online. Nien =========================================== Mails are checked daily and processed right away. If you don't get my replies within 3 days please send your mail again.