Re: Logical Logs on OWS 7.20 UC2

At 02:48 PM 9/8/97 EDT, you wrote: } }ramp wrote: }>=20 }> What i don=B4t know is what happen when the logical logs get full in a= not }> transactional evironment and with then devicel for logical logs set to }> /dev/null . I will get a dead lock or the logs get empty when On-Line }> need more space. } }If the LTAPEDEV=3D/dev/null then online acts as if ontape -a is always=20 }running and marks each log "backed up" as it is completed, in 7.xx+ the=20 }log is not actually freed until it is needed for reuse and can only be=20 }freed if there are not active transactions contained in that log. You=20 }can only get deadlocked on logs, in this case, if a single transaction=20 }spans all of the log files so that none can be freed when they are }needed=20 }for reuse. In a transaction environment you should have lots of large=20 }log files to prevent this. =20 } }A trick to let you unwind this problem if you do get hung up by long }transactions is to set LBU_PRESERVE=3D1 which will prevent the last log=20 }file from being used. Then if things to get stuck you can shutdown,=20 }change LBU_PRESERVE=3D0 and restart forcing a rollback of the hung=20 }transaction while freeing the last log file to record the rollback=20 }(credit Jake Salomon with this slight of hand) this will work if your=20 }log files are each large enough to record the fast recovery and rollback=20 }information. Once the offending transaction has rolled back all of the=20 }other log files will be freed. } }Art S. Kagel } What's the calculation to determine if you've got enough logspace to perform a rollback? For example, if I have only one session running and it's filling up my logs, and I have LTXHWM and LTXEHWM set to 30 and 40 (say), will I be assured that I have enough logspace to perform the rollback without crashing OnLine? My experience makes me think no (I had my production values set to 35 and 45, and my system still crashed), but I may have interpreted my situatuion incorrectly. Best regards, Nigel +-------------------------------------------------------------+ |Name : Edmund Nigel Gall Tel: (868) 636 3153 | |Title : Information Systems Specialist Fax: (868) 679 3770 | |Company: Process Plant Services Limited |=20 |Address: Atlantic Avenue, Point Lisas Industrial Estate | | Point Lisas, Couva, Trinidad & Tobago, W.I. | +----- mailto:nigelg@ppsl.com ------ http://www.ppsl.com -----+