tailieunhanh - A MANAGER’S GUIDE TO THE DESIGN AND CONDUCT OF CLINICAL TRIALS - PART 7

Các máy chủ sẽ làm giảm nguy cơ tham nhũng tập tin dữ liệu, bởi vì chỉ có máy chủ ghi vào cơ sở dữ liệu, một vụ tai nạn cúp điện cho khách hàng máy tính để bàn không thường xuyên xảy ra, sẽ không rời khỏi cơ sở dữ liệu trong một nhà nước không đầy đủ. | perform the operations. The server reduces the risk of data file corruption because only the server writes to the database a crash or power outage on a client desktop a not infrequent occurrence will not leave the database in an incomplete state. A database server takes advantage of the client-server architecture to lower network usage. Here is how this works If a client application were to open a file stored on a file server directly it would need to retrieve and transfer every record across the network just to filter out the ones it really needs. Instead the database server filters out the unneeded records and only sends out over the network the data that really matter. Microsoft s PC-based Access is a relational database but it is not a database server. MS-SQL SQL Anywhere DB2 and Oracle are both relational databases and database servers. One Size Does Not Fit All Bumbling s Clinical Affairs Department insisted that all studies use not only the same data management system but the same database construction the rationale being that this would further reduce development costs. Here s what actually happened The cost of developing the data analysis software doubled because of the constant need to extract and merge subsets before any analysis could be performed. Because so much of each file was waste space devoted to variables not in the current study retrieving the information proved enormously time consuming and almost brought the corporate mainframe to its knees. Information Systems kept buying larger and larger hard disks but invariably ran out of space as the files with their hundreds of dummy variables were an order of magnitude larger than they should be. The complex keying instructions that resulted when several pieces of information had to be combined into one to fit the standard design introduced a large number of errors that had to be corrected. Programmers had to work overtime during the analysis phase designing programs that would unpack the data that .