#50070: Unable to connect to the database
During my trek through Windows SharePoint Services I frequently hear about this error message. I like to refer to “Unable to connect to the database” as one of the dreaded errors of SharePoint. Why would I do this? Because in the majority of cases this is not a WSS problem. It comes from a variety of environmental factors which are difficult to diagnose and troubleshoot. Rather than get into a philosophical debate on the how or why of WSS error reporting in V2 it’s better to just list the causes that I know about.
- The Ad Hoc Query Plan bug. Most easily identified with SpSitemanager, first fixed and explained here.
- Speed & Duplex Settings NOT Specified for both the NIC and switch.
- NIC Drivers misconfigured or a bad NIC driver (no naming names).
- A damaged NIC or very rarely a bad/damaged network cable.
- Using one VLAN on the switch and then putting both the Internal NIC and the Public NIC on the same subnet.
- Unicast mode for WLBS without following the steps in the whitepaper or article. This results in the switch perceiving WLBS as port flooding.
- Multicast mode with WLBS without setting up a static ARP entry in the router/switch.
- Setting more than one Default gateway on a multi-homed server when both NIC’s are on the same subnet.
- Hardware based Load balancing not configured correctly. For an example on configuring this correctly see this.
- SynAttackProtect turned on after installing SP1 for Windows Server 2003. This is explained in the SQL Server 2005 release notes but affects SQL 2000 as well.
- Not using Aliases when accessing SQL on a port other than 1433.
- The SharePoint application pool account locked out.
- SQL Server Paused.
- A poorly architected web part behaving badly.
- High CPU on SQL from another application sharing the same server.
- Blocking on SQL server the result of backup software or another application.
- Anti-Virus gone awry. Corrected with SP2 for WSS.
- App Pool Recycling under load.
- Incorrect permissions in SQL server for the SharePoint App Pool account (Need Security Admin and Database Creators).
- NTLM Bottleneck see my previous posts for details.
I am certain there are other possible causes. The point is that many of these items are beyond the control of SharePoint. However, I am very pleased with the work the WSS Dev team has done with Beta 2 of V3. Many of the items listed above are caught and reported. I encourage you to try it for yourself.