Something interesting is going on. I wish I could show you the graphs, but I'm sure this will not be a surprise to the seasoned veterans.
A particular application server I have has been running for over a year now. I've been logging cpu load since mid-april. It took 8 months or more to fall from excellent performance to "acceptable." Then, over the course of about 5 weeks it fell from "acceptable" to "so-so." Then, in the last four weeks it's gone from "so-so" to alarming. I've been working on this performance drop since Friday but it wasn't until I replied to Arnau's post earlier today that I remembered I'd been logging the server load. I grabbed the data and charted it in Excel and to my surprise, the graph of the server's load average looks kind of like the graph of y=x^2. I've got to make a recomendation for a solution to the PHB and my analysis is showing that as the dataset becomes larger, the amount of time the disk spends seeking is increasing. This causes processes to take longer to finish, which causes more processes to pile up, which cuases processes to take longer to finish, which causes more processes to pile up etc. It is this growing dataset that seems to be the source of the sharp decrease in performance. I knew this day would come, but I'm actually quite surprised that when it came, there was little time between the warning and the grande finale. I guess this message is being sent to the list to serve as a warning to other data warehouse admins that when you reach your capacity, the downward spiral happens rather quickly. Crud... Outlook just froze while composing the PHB memo. I've been working on that for an hour. What a bad day. -- Matthew Nuzum www.bearfruit.org ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match