Rockwell Automation 6182 SDK - Manual (Page 16)

1–10 Introduction to the RAC6182
Publication 6182-UM002B-EN-P
The operating system boot process is responsible for merging the default
operating system Registry keys with the keys from the persistent
Registry. If the same keys exist, preference is given to the persistent
registry file. A few default keys are exceptions to this rule and are
bypassed during the merge; e.g. the O/S version number is acquired from
the O/S image.
The process of merging default and persistent registry information allows
operating system upgrades to add new registry keys and values and have
these be used in addition to any saved registry state. Since the saved
registry information has precedence, users’ saved registry keys for
control panel applets and other operating system items will be
maintained even in the case of operating system upgrades.
On the other hand, the priority given to persistent registry information
over default operating system registry information makes it possible for
applications or users to cause problems with operating system startup by
changing the wrong registry keys. When manipulating the RAC6182’s
CE Registry applications and users should exercise the same degree of
caution that would required in the case of a Windows 9x or NT device.
Important: Since some applications and drivers only read the Registry
at start-up, some registry changes made by applications
will have no effect until the RAC6182 is re-started.
Policies for When Registry Flushing Occurs
Control panel applets supplied with the operating system have been
customized to automatically flush the registry upon exiting the applet.
This allows users to change typical control panel settings such as
network, device name, screen saver, etc. and have these be flushed
without having to manually issue a registry flush to save these. Since the
flush occurs on applet exit as an optimization, users just need to
remember to close the applet after making changes for the automatic
flush to occur. Due to the inner workings of the applets, it is not feasible
to only flush on applet close if a value was changed, so a flush occurs on
applet close even if no registry values were actually altered.
Other applications such as Internet Explorer, remote networking, and any
third-party packaged applications are not customizable in this fashion
and hence changes they make to the registry will not be persistent until
some other application flushes the registry. To address this, two features
of the operating system are present.
First, an executable regflush.exe supplied with the system may be
manually executed by a user at any time to flush the registry to persistent
storage; this application simply calls RegistryFlush(). Second, upon a
controlled shutdown requested by an application through the
power/shutdown driver results in an automatic flush of the registry after
applications have signaled that their cleanup is complete and before the
hardware is actually shutdown or reset.