Part IV: Using Advanced Excel Features
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Understanding File Reservations
Networks provide you with the ability to share information stored on other computer systems.
Sharing files on a network has two major advantages:l It eliminates the need to have multiple copies of a file stored locally on user PCs.l (^) It ensures that the file is always up to date. For example, a group of users can work on a
single document, as opposed to everyone working on his or her own document and then
merging them.
Note
Some networks — generally known as client-server networks — designate specific computers as file servers.
On these types of networks, the shared data files are typically stored on the file server. Excel doesn’t care
whether you’re working on a client-server or a peer-to-peer network (where all the PCs have essentially equal
functions). n
Some software applications are multiuser applications. Most database software applications, for
example, enable multiple users to work simultaneously on the same database files. One user may
be updating customer records in the database, while another is extracting information for a report.
But what if two users attempt to change a particular customer record at the same time? Multiuser
database software contains record-locking safeguards that ensure that only one user at a time can
modify a particular record.
Excel, however, is not a multiuser application. When you open an Excel file, the entire file is
loaded into memory. If the file is accessible to other users, you wouldn’t want someone else to
change the stored copy of a file that you’ve opened. If Excel allowed you to open and change a file
that someone else on a network had already opened, the following scenario could happen.
Assume that your company keeps its sales information in an Excel file that is stored on a network
server. Esther wants to add this week’s data to the file, so she loads it from the server and begins
adding new information. A few minutes later, Jim loads the file to correct some errors that he
noticed last week. Esther finishes her work and saves the file. Later, Jim finishes his corrections
and saves the file. Jim’s file overwrites the copy that Esther saved, and her additions are gone.
This scenario can’t happen because Excel uses a concept known as file reservation. When Esther
opens the sales workbook, she has the reservation for the file. When Jim tries to open the file,
Excel informs him that Esther is using the file. If he insists on opening it, Excel opens the file as
read-only. In other words, Jim can open the file, but he can’t save it with the same name.
Figure 30.1 shows the message that appears if you try to open a file that is in use by someone else.