Re: Logical Logs problem

Hi, you have my sympathy! On Thu, 16 Jan 1997 odsharma@hclc.hclc-ggn.hcla.com wrote: ... > We are facing a problem quite frequently. Informix goes in 'recovery > mode' fails to become online saying that logical logs are full. Usually > this happens if server goes down due to some problem. Had the same thing with OnLine 5.03 (maybe more details in a later posting). > > We have 5 logical logs. Each logical log file is of size 1500K. > Size of logical log buffers is 32K. > Size of root dbspace is 20000 pages and a BlobSpace of 10000 pages ( > page size 2K). > "tbstat -l" shows 100% full for lal the logs. > Logical log tape device pathname & Archive tape device pathname is > /dev/null. Are you sure about this? If the logical log device is /dev/null, the logs should trundle away forever without any problem. > > When we try to take backup it just goes into a wait state and does not > come out. The status id shown as 'recovery' all the time. ( Device > /dev/null is working fine ) > > Is there a way out? Please help. A detailed reply including some > information on working Logical Logs would be appreciated. According to the OnLine Admin. Guide, the only way out is to restore from archive. Not good if it happens on a Monday evening and your last archive was on Friday night - 3 days of orders go down the drain, and loads of product comes in from the suppliers for unknown customers. However, if you have a support contract with Informix (or you're willing to pay them a hefty hourly rate) they can dial in and fix the problem with a C program. HOW THEY WORK: When one logical log fills up, the next one is started. When all transactions in the full log are completed, a checkpoint is written, and the log is backed up (to a DAT tape in our case). The problem occurs when a long transaction fills the logs. In this case the last log fills up, and the next log is the oldest full log (the one containing the start of the long transaction). Suddenly, Informix has nowhere to go, and grinds to a halt. If you add a logical log using tbmonitor, it is not necessarily added after the last full log, and in any case, is it not usable until after an archive. The C code that the Informix engineer used added logs after the last full one (with OnLine offline) so that when OnLine is restarted, it has more log space in which to roll back the transaction, and comes back online in the state at which the last log filled (no data loss). What annoyed me about this is that the manual does not say this can be done - if we hadn't disbelieved the manual and phoned for help, we would have just restored from tape (data loss, angry customers, etc - see above!). The situation that caused the logs to fill is even more laughable, but as I said, maybe more of that later. INFORMIX GURUS: I replied to this from personal experience - if any of the technical details are misleading, please correct me!! > > Thanks in advance. > O D Sharma > Cheers, Richard.