Retorno a una recuperación de un servidor SQL
In a previous newsletter we discussed the importance of Microsoft SQL server to businesses, how it is used, data loss situations specifically related to Microsoft SQL server and how they occur, and how Ontrack has the solution to recover missing or damaged Microsoft SQL server database files. In this issue, we will review the history of Microsoft SQL server, the server transaction process, and the levels of data loss. Finally, we’ll review Ontrack’s capabilities with these types of recoveries.
Microsoft SQL server was originally introduced in 1988 based on code licensed from Sybase. Microsoft continued development with the Sybase code until 1998, when they released Microsoft SQL 7.0 which was their first departure from the Sybase code and the start of Microsoft Data Engine. The current version of MS SQL is SQL 2000 which was released in February 2000, and Microsoft plans to release a new version this summer, Microsoft SQL 2005 (code name Yukon).
Microsoft SQL is a relational database that has the ability to store and process all kinds of data, including numbers, letters, characters, images and binary data. Microsoft SQL uses Transact-SQL, Microsoft’s version of Structured Query Language (SQL) for all of its decision-support applications.
A Microsoft SQL database typically consists of two files; the database, which typically has an extension of .MDF and the log which typically has an extension of .LDF. With Microsoft SQL 7.0 and higher, a user can create additional database and log files if needed. The additional database files have an extension of .NDF and the additional log files will have an extension of .LDF.
Microsoft SQL uses transaction processing to guarantee the consistency and recoverability of its databases. A transaction is the basic unit of work in a SQL server. Typically it consists of several SQL commands that read and update the database, but the update is not considered “final” until a COMMIT command is issued. Microsoft SQL server guarantees the atomicity of the database by using the transaction log to record all transactions before they are written. That way, if there is a failure, the system can recover the information from the logs, commit the missing transactions and resume normal functions. Atomicity means that each transaction is treated as all or nothing; it either gets written to the database in its entirety or not at all.
Data loss situations — What can happen?
Data loss situations can occur at a number of different levels. The first level of data loss starts with the storage device. This can be a single hard disk or a SAN or RAID storage array. If loss is at this level, Ontrack’s goal is get the storage device operational so that the data can be copied off. Ontrack’s cleanroom engineers work at an electronic and mechanical level to get the device operational. Due to the complex nature of storage arrays, SAN and RAID arrays add a challenging level to the complexity of the job. Ontrack has excelled in developing tools and specific techniques to handle these storage devices.
The second level of data loss can start at a file system level. The file system is a unique method of storing and organizing system and user files. The operating system controls the file system. If the information about where data files are on the volume is damaged or lost, then adjustments or repairs need to be completed at a file system level to access the data. Once the file system is repaired, the file’s data stream can be accessed correctly. Most operating systems have a utility that will automatically fix the file system. These utilities work to make the volume accessible, however, this can permanently damage the data stream of the file.
The third level of data loss can occur within the file itself. The internal structure can be corrupted to the point where the server application will no longer be able to read the file, and will no longer present it to the server. This is where Ontrack excels in providing a total data recovery solution.
Ontrack’s solution to Microsoft SQL data disasters
Ontrack has solutions for corrupted or damaged SQL database files. We can use our Remote Data Recovery™ technology to get the data back as fast as possible. Ontrack’s SQL recovery toolset was designed to retrieve the data contained within an .MDF file. We have recently expanded our capabilities to include the ability to recover data directly from the transaction logs for Microsoft SQL 7.0 and 2000 (.LDF files). So even if we are missing the database, we may still be able to completely recover the missing data from the log file.
The process of a SQL recovery begins with finding the database and log files requested. If the database file is inaccessible due to problems with the storage device, then we work to get that data extracted. If the file is missing, deleted or truncated due to problems with the file system, then we work to adjust or repair the file system to correctly point to the data stream of the file. And finally, if the file system has no pointers at all to the file, then we search the entire drive looking for SQL data.
The next stage is to work on the database and log files. This is where the SQL toolset comes into play. These tools analyze the complex internal structures of the .MDF and .LDF files and provide reports as to what tables are recoverable. The reports also list the number of data rows that will come back.
Once the evaluation is complete and authorization is given to recover the data, our SQL toolset will copy the data into another SQL server database. After this phase is complete, we can backup or archive the recovered data.
For those critical data loss situations where downtime is not an option, using our Remote Data Recovery technology gets the data back as fast as possible. As the fastest solution for SQL recoveries, Remote Data Recovery can copy the recovered data into a SQL server that is set up on your or your client’s site. They only need SQL server running. For best results, we recommend that the storage device we are working on be connected to a SQL server because all of the data transactions will be occurring on a single machine.
Below, please find a quick reference chart to Microsoft SQL and our data recovery capabilities. Whether you use our traditional In-Lab or our patented Remote Data Recovery solution, Ontrack has industry-leading solutions for SQL data loss. Contact Ontrack for all of your SQL recovery needs.
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