Sunday, November 11, 2007

Bad designed query made the whole system stop responding

It is bit boring this weekend coz I didn't arrange any thing to do and just stayed at home.
Anyway, Last friday, I was contacted by our helpdesk that our whole ERP system stop responding and everyone couldn't do anything on the system but wait. By running a check one the database, it turned out to be a query some ran causing the problem. I was bit confused initially coz the query was run from the application server. well, when I logoned to the app server later, I found out that one of my colleague was right there!
he was running a query to update one of the main table. the worst thing is, the query was made of 4 joins among 5 main tables and each of them is used intensively and contains hundreds of thousands of rows!
I believed that in such a situation, a 4 tables join is probably not a good option and can definitely cause big problem.

Tuesday, November 6, 2007

Building a SQL Server 2005 Cluster Lab with vmware, centos 4 & iSCSI software target

it is suprising that my old desktop machine (P4 3.0G, 2.5G RAM) has that much power to run 4 virtual machines at the same time.
the lab consisted of 1 win2k3 domain controller, 2 win2k3 cluster nodes and 1 centos 4 with iSCSI Enterprise Target acting as SAN. everything works great except that sometime the 'host only' nic won't start automatically and thus I have to start it manually.

Use ThinkVintage Fingerprint Reader software with Acer Laptop

Acer's fingerprint software doesn't work well, it slow down the laptop even though this is quite a powerful laptop with duo 2 core 2.0 GHZ CPU and 2G RAM. By uninstall Acer's fingerprint software and replacing it with ThinkVintage Fingerprint reader software, the laptop works much better now. Thinkpad & Acer Travelmate have the same fingerprint components, but I guess as long as you get fingerprint driver installed, the software should work the same.