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Suppose if the databases control file is lost permanently (no backup).
Can we retrieve the data from data file in Oracle database?
In general - 'yes'. But the circumstances matter. If you know what should be in the control file then you can recreate it (or rather, them; they should be multiplexed anyway) - see this article for example. That uses the create controlfile command with appropriate options and parameters to recreate the control file matching your existing data files. Really make sure you understand what it's doing and what impact it may have - you don't want to make things worse than they already are.
Or google for "oracle recover control file".
Don't rely on this being possible though - it's no substitute for a real backup and recovery strategy.
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Basically my application needs to dump data daily into a database. But for any data written down, there is no need to update.
Hence, is appending to csv or json file sufficient for the purpose. Or it will be more computationally efficient to write in standard SQL?
Edit
Use-Case Update
I am expecting to store one entry of for each particular activity count daily. There are about 6-8 activities.
It is exactly like a log in some sense. I would like to perform some analysis with the trend of activities for example. There is no relations between different activities though.
If say in some cases there might be a need for update, would that imply a proper database will be more suitable rather than text file?
It depends on the nature of the data, but there may be another style of database other than an SQL one which could be suitable, like MongoDB which essentially stores JSON objects.
SQL is great when you need entities to have relationships to each other, or if you can take advantage of the type of select queries it can provide you with.
Database systems do have some overhead and could have some gotchas you might not expect, like loading up a heap of crap into memory so it's ready to be searched.
But storing text files can have drawbacks, like it might become difficult to manage your data in the future.
It basically sounds like your use-case is similar to logging, in which case dumping it into a file is fine.
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I was just wondering if I change column names on tables in SQL Server will they effect my SSIS packages.
Yes it would, the source component would fail with a "Component (1) failed validation and returned validation status VS_NEEDSNEWMETADATA".
Sure will and they can be painful and time consuming to fix. You may need to go through steps all through the data flow not just the intial one or the final one (depending on whether you are changing the source or destination). Unions in the dataflow can be a particular pain point. If you want the change to reflect in a file you are creating, you may need to revisit the connection as well.
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Maybe many of you have wasted a lot of time on this when backup or restore a database using SQL Server 2008
Every time it comes back to the default location, and the form doesn't have a browse button, moreover, when pasting a URL the tree doesn't refresh, So it forcing you to walk though the Tree to find the location or to prepare your URL and file name manually and then paste it.
My question, Is there any technical reason that makes it very hard to have this simple functionality in such important form.
I have submitted a feedback ticket about it Here, please vote up if you think that a browse functionality should be there.
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There are many file shredders programs that one can use in order to delete permanently one file. What I want to know is some implementation details. For example, considering Gutmann algorithm, how it should work with file and file system? Should an application iterate over all hdd cluster in order to overwrite them? Or it will be enough to open one file, change it content in some way and after that to delete it?
Vice versa, how to restore deleted file? I have not found a lot of information for these topics.
I will be very thankful for your replies.
You could look at the source code of the shred utility which is a part of the GNU core utils found on Linux.The basic idea is to make multiple passes over the disk blocks.There are also some assumptions made about the way the underlying files system commits these writes. See info coreutils 'shred invocation' for more information.
Restoring deleted files are done best when you know the internal layout of the file system in question and how the delete operation is implemented on it. For example, many drivers for the FAT file system just mark the directory entry as deleted but leave the file's content in tact. (Until and unless it is over-written by new files that you create). So you could just take a dump of the disk and scan through the raw data looking for what you want.
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Is it a custom database, or are they using a 'classic' triple store ?
Chasing some old posts, I found this message on their board, followed by this response to a query directed at the developer mentioned in the first message.
While I doubt the developer's response is the mentioned 'long post' of the first, it notes:
"We have written our own graph database on top of Unix. We don't have an RDBMS or OODB storage layer because conventional databases don't handle the volume of self-joins that graph queries generate. Persistence is via memory mapped files with our own transaction manager, custom tailored to provide exactly the (minimal) ACID requirements that we have."
So unless freebase.com have changed their back end tools since Jan '08, it's a custom database.