5-25Lesson 3 Configuring System Settings
Professional. Select System Cache if you are using your computer as a server or if the
programs you are running require a large system cache.
Virtual Memory For virtual memory, Windows XP Professional uses a process called
demand paging to exchange data between random access memory (RAM) and paging
files on the hard disk. When you install Windows XP Professional, Setup creates a
virtual-memory paging file, PAGEFILE.SYS, on the partition in which you installed
Windows XP Professional. The default or recommended paging file size for Windows XP
Professional is equal to 1.5 times the total amount of RAM. For best results, never set
the value of the paging file size to less than the recommended amount. Typically, you
can leave the size of the paging file set to the default value and let Windows XP Pro-
fessional manage the file size. In some circumstances, such as when you run a large
number of applications simultaneously, you might find it advantageous to use a larger
paging file or multiple paging files.
!
Exam Tip By default, Windows XP manages the paging file size, but you can designate a
file size for special circumstances. The recommended paging file size is equal to 1.5 times
the total amount of RAM.
To configure the paging file, in the Performance Options dialog box, click the Change
button in the Virtual Memory section. The Virtual Memory dialog box (see Figure 5-10)
identifies the drives in which the paging files reside and allows you to modify the
paging file size for the selected drive.
F05us10.bmp
Figure 5-10
Configure paging file settings in the Virtual Memory dialog box.
Important Only users with administrative rights can use the Performance Options dialog
box to increase the paging file size.
Paging files never decrease below the value found in the Initial Size text box that was
set during installation. Unused space in the paging file remains available to the internal
Windows XP Professional Virtual Memory Manager (VMM). As needed, a paging file
grows from its initial size to the maximum configured size, which is listed in the Max-
imum Size text box. When a paging file reaches the maximum size, but a running pro-
gram still needs to allocate more virtual memory, Windows XP Professional will refuse
that allocation, which can cause an error, or even a crash, in applications.
When you restart a computer running Windows XP Professional, the system resizes all
paging files to the initial size.
Data Execution Prevention
Data Execution Prevention (DEP) is a set of hardware and software technologies that
perform additional checks on memory to help prevent malicious code from running on
a computer. In Windows XP Professional, DEP can be enforced by compatible hard-
ware and by software.
Note DEP is an update included with Windows XP Service Pack 2. Hardware DEP is avail-
able with compatible devices and runs only on the 32-bit version of Windows XP Professional
and Home Edition.
Hardware DEP works by marking all pages in memory as non-executable unless the
page explicitly contains executable code. This process helps prevent malicious
attacks that try to insert and run executable code into memory. To use hardware DEP,
a computer must have a compatible processor that allows Windows to mark memory
pages as non-executable. Both Intel and AMD provide hardware DEP–compatible
processors.
Software DEP is a set of security checks that can run on any processor capable of run-
ning Windows XP. However, the security provided by software DEP is limited com-
pared to that provided by hardware DEP.
You can configure DEP by using the Data Execution Prevention tab of the Performance
Options dialog box. By default, DEP is enabled for only essential Windows programs
and services. However, you can turn DEP on for all programs and services, and then
select specific programs and services for which you do not want DEP enabled.
Bạn đang xem 5 - - MICROSOFT PRESS MCSA MCSE SELF PACED TRAINING KIT EXAM 70 270 PHẦN 2 PPSX