TAILIEUCHUNG - SQL Server Tacklebox- P44

SQL Server Tacklebox- P44: This book, as with almost all books, started out as an idea. I wanted to accumulate together those scripts and tools that I have built over the years so that DBAs could sort through them and perhaps adapt them for their own circumstances. | 8 Finding data corruption Corruption on data pages We know that our one table in the neo database is a heap so any corruption we induce is going to be directly on the data pages rather than on any nonclustered index. The latter case is actually more favorable as the data in the index is a duplicate and so it is relatively easy to repair the damage. We ll cover this latter case after we ve looked at inducing and hopefully recovering from corruption of the data in our heap table. Putting a Hex on the data There are many hexadecimal editors out there in the world many of them free or at least free to try out. For this chapter I downloaded a trial version of one called ironically Hex Editor Neo by HHD Software. What a Hexadecimal editor allows the DBA to do is simply open and view the contents of a file in this case the data file. While it is an interesting exercise I would only recommend it for testing or training purposes as it is a very dangerous tool in inexperienced hands. What I want to do here is use this hexadecimal editor to zero out data in a single database file in fact in a single data page. This will cause the required corruption mimicking a hardware problem that has caused inconsistent information to be written to disk without making the database unreadable by SQL Server. And though I have not stated it heretofore . Do not go any further without first backing up the database The data that I am fixing that is a Southern expression to zero out resides on the data page revealed in Figure namely 1 184. In order to corrupt the data on this page I first need to shutdown SQL Server so that the parent data file C Program Files Microsoft SQL Server MSSQL Data is not in use. Next I simply open Hex Editor Neo and find the location of the one record with neoid 553 and neotext UVWXYZ that we identified using the dbcc PAGE previously. Most hexadecimal editors Hex Editor Neo included have the ability to search for values within the data file. Here .

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