I am living in Pakistan and it is very hard to get the latest information. Would you please help me to investigate the role of time in a database? There is an implicit assumption that databases should be an accurate reflection of current reality. However, we also observe that database systems provide mechanisms to change their date, i.e. the current reality alters with the passage of time.
Here are some elements that may be of use. Following what happens that a bit of information over time is, I feel, very important. There are many ways about it, but I will list two. The first one is to rely on IBM file journals, but it can be difficult and not very efficient in terms of space and quality of information. Journal receivers are typically kept for one week, and carry quite a lot of data only useful to support commitment control or crash recovery.
The other is to have "audit" file(s). This file would store a key to link to the file it audits, a timestamp to know when a change was made, the previous situation of the record (and possibly the new) and an explanation as to why the change was made. Also useful is the detail of what process or program caused the change. Such files do not need to be permanent. You may decide to keep records in such a file for a maximum of 1 month, and to do so you would use the timestamp to delete records older than 1 month. There are space considerations to be made, but the benefit of having such information at hand is invaluable. I found out that again in the latter part of last week and yesterday when changes I made to the software in our company went wrong. Thanks to the audit file, it took me a few minutes to sort the problem out and even more importantly, to give a list of problems to the relevant departments.
Best wishes from Croydon, UK
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