> > > Hi Richard! > The log only contains all transactions (since the last database backup) > when running in rollforward mode. When running in normal mode, only > uncommitted transactions are written to the log. As soon as a > transaction is completed, the transaction is committed to the database > and thus removed from the log.
We're probably saying the same thing ;-) . . . here is how I understand the log to work. My understanding is that the log is a logical sequential-circular file with a head (where new trans are written) and tail(the oldest uncommitted tran). As trans are created they are written to the head (uncommitted). As trans complete (commited), commits are written to the log. Thus tsm knows what to do after a crash - needing everything from head to tail to put the db back into a consistent state. When replaying the log committed trans can be ignored, and uncommitted trans can be rolled back. The space used by committed trans between the head and tail is _not_ reusable. Usable space is what is in front of the head up to the tail. As the oldest tran commits, the tail is pulled forward. If any one tran remains uncommitted long enough for the head to come all the way around and but into the tail . . . you filled the log. In a sense, committed trans are like expired files on tape that need reclamation before the space is reusable. I thought the difference going to roll-forward mode is that the log tail is pinned at the last backup. The tail is not moved up until a backup has completed. While is normal mode the tail moves forward as the oldest tran commits. In a sense, the log is always pinned, but the pinning tran is always changing as trans commit. So I see logpin _problem_ as being caused by two issues: 1) Some long running (slow) tran keeping the tail pinned. 2) The rate new trans are added and move the head ever forward toward the tail. That's my understanding how it works . . . which could be very wrong! Rick ----------------------------------------- The information contained in this message is intended only for the personal and confidential use of the recipient(s) named above. If the reader of this message is not the intended recipient or an agent responsible for delivering it to the intended recipient, you are hereby notified that you have received this document in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. If you have received this communication in error, please notify us immediately, and delete the original message.
