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.
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The Ad Hoc Query Plan bug. Most easily identified with
SpSitemanager, first fixed and explained
here.
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Speed & Duplex Settings NOT Specified for both the NIC and switch.
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NIC Drivers misconfigured or a bad NIC driver (no naming names).
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A damaged NIC or very rarely a bad/damaged network cable.
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Using one VLAN on the switch and then putting both the Internal NIC and the Public NIC on the same subnet.
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Unicast mode for WLBS without following the steps in the
whitepaper or
article. This results in the switch perceiving WLBS as port flooding.
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Multicast mode with WLBS without setting up a static ARP entry in the router/switch.
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Setting more than one Default gateway on a multi-homed server when both NIC’s are on the same subnet.
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Hardware based Load balancing not configured correctly. For an example on configuring this correctly see
this.
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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.
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Not using
Aliases when accessing SQL on a port other than 1433.
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The SharePoint application pool account locked out.
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SQL Server Paused.
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A poorly architected web part behaving badly.
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High CPU on SQL from another application sharing the same server.
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Blocking on SQL server the result of backup software or another application.
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Anti-Virus gone awry. Corrected with SP2 for WSS.
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App Pool Recycling under load.
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Incorrect permissions in SQL server for the SharePoint App Pool account (Need Security Admin and Database Creators).
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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.
