Notes on SQL

Random articles from a puzzled DBA

Background
Whilst reading up on the finer details of High Availability Groups (HA Groups) I have discovered that it can, under certain circumstances, use Snapshot Isolation Level and therefore, row versioning. This has implications with your monitoring and maintenance tasks.
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Having attempted to start an old test instance from SQL Server Configuration Manager, I received the wonderful error “The request failed or the service did not respond in a timely fashion. Consult the event log or other applicable error logs for details

Error From Configuration Manager

More helpful than some message you can get – at least it tells me where to look.

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A column set is an untyped XML column that can be used to update and select all sparse columns defined in the associated table. This XML is not physically stored in the table – it is in effect a calculated column that can be used to update.
Microsoft recommend its use for tables that contain a large number of sparse columns, although it is not without its overheads.
It has some interesting effects upon updates and selects, for the table that uses it.

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