Re: Un-attended Large Archives (fwd)

In <1993May12.171859.1170@informix.com> davek@newjersey.informix.com (Dave Kosenko) writes: >Graeme Sargent writes: >|> Are you saying that the tape management subsystem and/or other 6.0 >|> features will remove the checkpoint/online-archiving/tape change lockup??? >If you have only one drive, and have to manually change the tape, then no. >The very basic mechanisms of how on-line archiving is implemented require >that a checkpoint wait for the archive process to verify that all the needed >pages from the physical log have been read by the archive before emptying >the physical log (the last phase of a checkpoint). If the archive process >is waiting for a tape change, it will hold the checkpoint from completing. >What it WILL do is allow you to specify multiple backup devices so that when >one fills, the other will be used automatically, and so on (for however >many devices you specify). We have equivalent functionality already on Pyramid, in the form of our FastTRAC virtual tape software. However, I consider it unacceptable for an OLTP service provider to *require* that archive media be changed within minutes (or seconds) of the previous volume filling in order that an OLTP service continue to be provided. There should be a grace period of a small number of hours (or at least a large number of minutes) before throughput is affected. And one should not have to compromise other requirements, such as fast Fast Recovery, in order to achieve this. I understand *why* the handshaking requirement exists between tbtape and the checkpoint, but I believe that the responsibility to provide a workaround, such as a buffer, should lie with OnLine's designers rather than implementors such as Anasazi or ourselves. graeme -- Disclaimer: The author's opinions are his own, and not necessarily those of Pyramid Technology Ltd. or Pyramid Technology Inc. --------------------------------------------------------------------------- -m------- Graeme Sargent Voice: +44 (0)252 373035 ---mmm----- Senior Database Consultant Fax : +44 (0)252 373135 -----mmmmm--- Pyramid Technology Ltd. Telex: Tell who??? -------mmmmmmm- Farnborough, Hants GU14 7PL Email: graeme@pyra.co.uk --------------------------------------------------------------------------- We have the technology. The tricky bit is learning how to use it.