U.S. patent application number 09/812743 was filed with the patent office on 2001-08-02 for method and apparatus for detecting system configuration changes.
Invention is credited to Blumenau, Steven M., Cohen, Steven, Madden, John F. JR..
Application Number | 20010011348 09/812743 |
Document ID | / |
Family ID | 22785697 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010011348 |
Kind Code |
A1 |
Blumenau, Steven M. ; et
al. |
August 2, 2001 |
Method and apparatus for detecting system configuration changes
Abstract
Method and apparatus for detecting changes in a configuration of
a computer system including a host computer and at least one
computer system resource. Information relating to a reference
configuration of the computer system is stored at a first point in
time. A current configuration of the computer system is determined
at a second point in time. The current configuration of the
computer system is compared with the reference configuration to
determine whether the current configuration differs from the
reference configuration. An indication is provided when the current
configuration of the computer system differs from the reference
configuration.
Inventors: |
Blumenau, Steven M.;
(Holliston, MA) ; Cohen, Steven; (Westboro,
MA) ; Madden, John F. JR.; (Holden, MA) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, PC
FEDERAL RESERVE PLAZA
600 ATLANTIC AVENUE
BOSTON
MA
02210-2211
US
|
Family ID: |
22785697 |
Appl. No.: |
09/812743 |
Filed: |
March 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09812743 |
Mar 20, 2001 |
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09211131 |
Dec 14, 1998 |
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6240511 |
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Current U.S.
Class: |
713/100 ;
713/1 |
Current CPC
Class: |
G06F 9/4411
20130101 |
Class at
Publication: |
713/100 ;
713/1 |
International
Class: |
G06F 015/177 |
Claims
1. In a computer system including a host computer and at least one
computer system resource, a method of detecting changes in a
configuration of the computer system, the method comprising steps
of: (A) storing information relating to a reference configuration
of the computer system at a first point in time; (B) determining a
current configuration of the computer system at a second point in
time; (C) comparing the current configuration of the computer
system with the reference configuration to determine whether the
current configuration differs from the reference configuration; and
(D) providing an indication when the current configuration of the
computer system differs from the reference configuration.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of Ser. No. 09/211,311,
entitled METHOD AND APPARATUS FOR DETECTING SYSTEM CONFIGURATION
CHANGES, filed Dec. 4, 1998, now pending.
FIELD OF THE INVENTION
[0002] The present invention is directed to a method and apparatus
for detecting changes in a configuration of a computer system.
DESCRIPTION OF THE RELATED ART
[0003] Many computer systems include one or more host computers and
one or more system resources that are accessible thereby. An
example of such a computer system is shown in FIG. 1, and includes
a host computer 1 and a storage system 3 that serves as a system
resource accessible by the host computer 1. The storage system 3
includes a plurality of storage devices on which data are stored.
In the exemplary system shown in FIG. 1, the storage system 3
includes a plurality of disk drives 5a and 5b and a plurality of
disk controllers 7a-7b that respectively control access to the disk
drives 5a and 5b. The storage system 3 further includes a plurality
of storage bus directors 9a-d that control communication with the
host computer 1 over communication buses 17a-d. Communications
buses 17a-d interface to the storage system 3 through ports 18a-d.
Finally, the storage system 3 includes an internal bus 13 over
which the storage bus directors 9a-d and the disk controllers 7a-7b
communicate.
[0004] The host computer 1 includes a processor 16 and one or more
host bus adapters 15a-d that each controls communication between
the processor 16 and the storage system 3 via a corresponding one
of the communication buses 17a-d. It should be appreciated that
rather than a single processor 16, the host computer 1 can include
multiple processors. Each of the buses 17a-d can be any of a number
of different types of communication links, with each of the host
bus adapters 15a-d and the storage bus directors 9a-d being adapted
to communicate using an appropriate protocol for the communication
bus coupled between them. For example, each of the communication
buses 17a-d can be implemented as a SCSI bus, with the directors
9a-d and adapters 15a-d each being a SCSI driver. Alternatively,
communication between the host computer 1 and the storage system 3
can be performed over a Fibre Channel fabric, where the buses 17a-d
are Fibre Channel links.
[0005] As shown in the exemplary system of FIG. 1, some computer
systems employ multiple paths for communicating between the host
computer 1 and the storage system 3 (e.g., each path includes one
of the host bus adapters 15a-d, one of the buses 17a-d, one of the
ports 18a-d, and one of the storage bus directors 9a-d in FIG. 1).
In some such systems, each of the host bus adapters 15a-d has the
ability to access each of the disk drives 5a-b, through an
appropriate storage bus director and disk controller.
[0006] FIG. 2 is a schematic representation of a number of mapping
layers that may exist in a computer system such as the one shown in
FIG. 1. The mapping layers include an application layer 21 which
includes application programs executing on the processor 16 of the
host computer 1. The application layer 21 will generally refer to
data objects used thereby with a label or identifier such as a file
name, and will have no knowledge about where the corresponding file
is physically stored on the storage system 3 (FIG. 1). In addition,
the host computer 1 also includes a file system and/or logical
volume manager (LVM) layer 23 that maps each data object specified
by the application layer 21 to a particular logical volume (that
the host computer 1 perceives to correspond to an actual physical
storage device) wherein the data object is stored. The file
system/LVM layer 23 will generally refer to a logical volume (also
referred herein as a "raw storage device") using a label or
identifier that is at least partially descriptive of a physical
component of the computer system that is used by the host computer
1 when accessing the logical volume. The physically descriptive
information may include, for example, information descriptive of
the one of the multiple paths via which the logical volume may be
accessed, as well as a unique identifier for the raw storage
device. For example, for a SCSI connection, the device identifier
"/dev/dsk/c0t0d0" may be used to refer to a raw storage device or
logical volume accessible at a channel zero (c0) (which can be any
of the multiple paths in FIG. 1), and having a target number zero
(t0) and a logical unit number (LUN) zero (d0) that together
uniquely identify the raw storage device.
[0007] Below the file system/LVM layer 23 is a multi-path mapping
layer 25 that maps the logical volume address specified by the file
system/LVM layer 23, through a particular one of the multiple
system paths, to the logical volume address to be presented to the
storage system 3. Thus, the multi-path mapping layer 25 not only
specifies a particular logical volume address, but also specifies a
particular one of the multiple system paths used to access the
specified logical volume.
[0008] If the storage system 3 were not an intelligent storage
system, the logical volume address specified by the multi-pathing
layer 25 would identify a particular raw physical device (e.g., one
of the disk drives 5a-b) within the storage system 3. However, in
an intelligent storage system such as that shown in FIG. 1, the
storage system itself may include a further mapping layer 27, such
that the logical volume address passed from the host computer 1 may
not correspond directly to an actual physical device (e.g., a disk
drive 5a-b) in the storage system 3. Rather, a logical volume
specified by the host computer 1 can be spread across multiple
physical storage devices (e.g., disk drives 5a-b) or multiple
logical volumes accessed by the host computer 1 can be stored on a
single physical storage device.
[0009] As discussed above, application programs running in the
application layer 21 typically access logical volumes within the
storage system 3 via the file system/LVM layer 23, which uses
device identifiers for the logical volumes that include information
descriptive of a physical component of the computer system through
which the logical volumes are accessed. This can cause problems
when changes are made to the physical configuration of the computer
system. User flexibility in reconfiguring a computer system has
become more and more prevalent with the advent of Fibre Channel.
Fibre Channel is a communication protocol that enables computer
system components that were previously incapable of communicating
to be coupled together in a manner that enables communication
therebetween. For example, using Fibre Channel a first computer
system resource that communicates using SCSI can communicate with a
second computer system resource that communicates using Ethernet.
An example of a computer system implemented using Fibre Channel is
shown in FIG. 4, wherein a host computer 1 is coupled to a storage
system 3 via a Fibre Channel cloud 100. It should be appreciated
that the Fibre Channel cloud 100 can include a number of switching
and hub components, such that the host computer 1 and the storage
system 3 can communicate with other system components via the cloud
100.
[0010] It should be appreciated that when the computer system of
FIG. 4 is brought on line, the host computer 1 will be booted or
initialized, and will go through a process of assigning device
identifiers (e.g., "/dev/dsk/c0t0d0" as discussed above), to each
raw storage device or logical volume accessible to the host
computer through the Fibre Channel cloud 100. It should be
appreciated that the assignment of a particular one of the
communication paths 102a-d as channel c0 is fairly arbitrary, and
is not initially significant, so long as each of the paths 102a-d
is assigned a unique channel number. Referring to the illustrative
example shown in FIG. 4, during initialization, the communication
path 102a initially may be assigned channel designation c0 and
communication path 102b initially may be assigned channel
designation c1. A first logical volume 104 is made visible to the
Fibre Channel cloud 100 over a port (not shown) of the storage
system 3 that is coupled to path 102a, and a second logical volume
106 is made visible via a port (not shown) coupled to path 102b.
Thus, during initialization, the logical volume 104 may be
identified by an operating system on the host computer 1 using a
device identifier "/dev/dsk/c0t0d0," and the logical volume 106 may
be identified using the device identifier "/dev/dsk/c1t0d0".
[0011] It should be appreciated that events can occur that may
change the physical configuration of the computer system shown in
FIG. 1, which may require a rebooting of the host computer 1. For
example, one such reconfiguration change may be caused by a failure
of the port on the storage system 3 that is coupled to the path
102a. If such a failure were to occur, the storage system 3 can be
reconfigured so that the logical volume 104 can be exported from
the storage system 3 over the port coupled to the path 102b. Thus,
after reconfiguration of the storage system 3, the host computer 1
would generally need to be rebooted to recognize the reconfigured
nature of the computer system. In doing so, it should be
appreciated that the path 102a will no longer be recognized, such
that upon reinitialization, a different channel number may be
assigned to each of the paths 102b-f. For example, the path 102b
may be the first channel recognized by the host computer 1 when it
reboots, causing this channel to now be identified as channel c0.
As a result of this reinitialization, the device identifier for
logical volume 106 could change to "/dev/dsk/c0t0d9", and the
device identifier for logical volume 104 could change to
"/dev/dsk/c0t1d0".
[0012] As discussed above, the file system LVM layer 23 executing
on the host computer 1 accesses a particular logical volume using
the device identifier assigned by the operating system. However, it
should be appreciated that as a result of the change to the
physical configuration of the computer system, the device
identifier for each of the logical volumes 104 and 106 will have
changed between the time when the host computer 1 was initially
booted, and the time when it is rebooted following the change in
the physical configuration of the system. It should be appreciated
that this can cause significant problems for applications executing
on the host computer 1. For example, an application program that is
executing on the host computer 1 and that stores a particular data
file in logical volume 104. After the reconfiguration of the
storage system 3 and the resulting reboot of the host computer 1,
the device identifier previously used by the file system/LVM
mapping layer 23 to access logical volume 104 (e.g.,
"/dev/dsk/c0t0d0" in the example discussed above) will now, unknown
to the application program, actually map to the logical volume 106.
Therefore, when performing reads, the application program will
actually read the wrong data, and when performing writes, the
application program will be overwriting the wrong data in the
storage system 3.
[0013] It should be appreciated from the foregoing that the use of
device identifiers that include information that is dependent upon
a physical component of the computer system used to access the
logical volume or raw storage device can lead to problems when the
system is reconfigured, because the device identifiers for one or
more logical volumes can change in a manner that is typically not
communicated to the application layer 21 (FIG. 2). This can result
in the wrong data being accessed for a read or write, or can result
in a logical volume becoming inaccessible to an application program
which is not capable of accessing the logical volume via its new
device identifier.
SUMMARY
[0014] One illustrative embodiment of the invention is directed to
a method of detecting changes in a configuration of a computer
system including a host computer and at least one computer system
resource. The method comprises steps of: (A) storing information
relating to a reference configuration of the computer system at a
first point in time; (B) determining a current configuration of the
computer system at a second point in time; (C) comparing the
current configuration of the computer system with the reference
configuration to determine whether the current configuration
differs from the reference configuration; and (D) providing an
indication when the current configuration of the computer system
differs from the reference configuration.
[0015] Another illustrative embodiment of the invention is directed
to a computer readable medium encoded with a program for execution
on a host computer in a computer system including the host computer
and at least one computer system resource. The program, when
executed on the computer, performs a method of detecting changes in
a configuration of the computer system, the method comprising steps
of: (A) storing information relating to a reference configuration
of the computer system at a first point in time; (B) determining a
current configuration of the computer system at a second point in
time; (C) comparing the current configuration of the computer
system with the reference configuration to determine whether the
current configuration differs from the reference configuration; and
(D) providing an indication when the current configuration of the
computer system differs from the reference configuration.
[0016] A further illustrative embodiment of the invention is
directed to a host computer for use in a computer system including
the host computer and at least one computer system resource. The
host computer comprises: storing means for storing information
relating to a reference configuration of the computer system at a
first point in time; determining means for determining a current
configuration of the computer system at a second point in time;
comparing means for comparing the current configuration of the
computer system with the reference configuration to determine
whether the current configuration differs from the reference
configuration; and providing means for providing an indication when
the current configuration of the computer system differs from the
reference configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a block diagram of an exemplary computer system on
which aspects of the present invention can be implemented;
[0018] FIG. 2 is a schematic representation of a number of mapping
layers that exist in a known computing system;
[0019] FIG. 3 is a block diagram of a host computer including
elements suitable for implementing an embodiment of the present
invention; and
[0020] FIG. 4 is a block diagram of a Fibre Channel computer
system.
DETAILED DESCRIPTION
[0021] In accordance with one illustrative embodiment of the
invention, a method and apparatus is provided to detect changes in
a configuration of a computer system, and to provide an indication
that changes to the configuration of the computer system have been
detected. This can be done in any number of ways, and the present
invention is not limited to any particular implementation. In
accordance with one embodiment of the invention, information
relating to a known configuration of the computer system is stored
at a reference point in time. Thereafter (e.g., in response to a
rebooting of the host computer), a current configuration of the
computer system is determined. The current configuration of the
computer system is compared with the reference (stored)
configuration of the computer system to determine whether the
current configuration differs from the reference configuration, and
when it does, an indication of this difference is provided.
[0022] Information relating to a reference configuration of the
computer system may be gathered in any of numerous ways, and the
present invention is not limited to any particular implementation.
In one embodiment of the invention shown in FIG. 3, a configuration
capture program 30 is provided on the host computer 1. When a user
determines that the computer system is configured properly, the
user may instruct the configuration capture program 30 to collect
and store information relating to the then current configuration of
the computer system at that reference point in time. As discussed
below, this stored information can be used to identify a reference
configuration. The configuration capture program 30 may store the
information descriptive of the reference configuration in any of
numerous ways and on any type of storage medium. For example, the
information can be stored in a configuration file 32 on an hard
disk 34 internal to the host computer 1.
[0023] The configuration capture program 30 may, for example,
collect configuration information descriptive of the current
configuration of the computer system in any of numerous ways. For
example, the configuration capture program 30 may obtain from the
operating system 36 of the host computer 1 the unique identifier
for each device accessible by the host computer 1. The operating
system 36 of the host computer 1 will typically maintain a device
directory 38 including information descriptive of each device which
the operating system 36 recognizes as being accessible by the host
computer. Each device identifier typically includes information
descriptive of a physical path, port, or link by which the host
computer accesses the device. For example, the device identifier
"/dev/dsk/c1t0d0" may be the device identifier of a device that is
accessed by the host computer 1 on channel number one (c1), and has
a target number (t0) and LUN (dO) zero within the storage system
3.
[0024] Once the configuration capture program 30 has the device
identifier for a device, it may use the identifier to access the
device for the purpose of obtaining additional information
pertaining thereto. The additional information that the capture
program 30 can access for a particular device will vary depending
upon the nature of the system resource. Thus, the present invention
is not limited to accessing additional information of any
particular type. In accordance with one illustrative embodiment of
the invention, it is desirable to retrieve additional information
that uniquely identifies the device in a manner that is not
dependent upon the physical configuration of the computer system.
For example, when the computer system resource is a storage system
3 such as that shown in FIG. 1, the configuration capture program
30 may use a device identifier to access from the storage system 3
information that uniquely identifies the raw storage device or
logical volume corresponding thereto. In a storage system 3 such as
that shown in FIG. 1, each logical volume will typically include a
label that is unique within the storage system 3 and identifies the
logical volume. However, it should be appreciated that in some
computer systems, multiple storage systems 3 may be accessible by
the host computer 1. To handle such a system configuration, each
storage system 3 may also be provided with a unique identifier
(e.g., a serial number), such that each logical volume in the
computer system can be identified by the serial number of the
storage system in which it is included, in conjunction with the
unique identifier of the logical volume within that storage
system.
[0025] After the additional information is retrieved from the
device to identify it in a manner that is independent of the
physical configuration of the computer system, the configuration
capture program 30 may store that information in a manner that is
associated with the corresponding device identifier that the
operating system uses to identify that device in the current
configuration of the system. This can be done for each device
accessible to the host computer 1 (e.g., for each device in the
device directory 38). This associated data set can be stored in the
configuration file 32 and serves to identify the reference
configuration, which can be used for comparison purposes in a
manner discussed below.
[0026] As discussed above, it is possible that the configuration of
the computer system will change after the configuration file 32 is
saved. For example, as mentioned previously, one of the ports 18a-d
on the storage system 3 may malfunction, causing the port and
storage devices normally accessible through that port to become
inaccessible to the host computer 1. Another exemplary way in which
the configuration of the computer system may change is that the
links between the host computer 1 and the storage system 3 may be
reconfigured. Yet another exemplary way in which the configuration
of the computer system may change is that logical volumes within
the storage system 3 may be added, removed, or exported through a
different port on the same or another storage system, thereby
causing the contents of the host computer's operating system device
directory 38 to change. In the case where a logical volume within
storage system 3 moves, a logical volume which was previously
accessible using a particular channel, target, and LUN will no
longer be accessible using that identifier, but rather will be
accessible at a different channel, target, and LUN. However, as
discussed above, application programs on the host computer 1 will,
via the file system/LVM mapping layer 23, continue to access the
logical volume using the old channel, target and LUN identifier,
which can cause problems. For example, if no logical volume is
accessible at the old channel, target and LUN, any attempt to
access the logical volume at that channel, target and old
identifier will result in an error. Even worse, if a different
logical volume is now accessible at that channel, target and LUN,
as in the example discussed above, attempts to read from the
logical volume will result in reading the wrong data, and attempts
to write to the logical volume will result in writing data to the
wrong logical volume.
[0027] In one illustrative embodiment of the present invention,
changes to the configuration of the computer system are detected
and an indication that the configuration of the computer system has
changed is provided. This detection can be done in numerous ways.
For example, the host computer 1 can be provided with a
configuration comparison program 40 that can compare the current
(i.e., at the time the program is run) configuration of the
computer system with the reference configuration (stored in the
manner discussed above) to determine whether any changes have
occurred. The configuration comparison program 40 can be executed
whenever it is desired to check the configuration of the system. In
accordance with one embodiment of the invention, the comparison
program 40 is executed each time the host computer 1 is rebooted,
but it should be appreciated that the present invention is not
limited in this respect. The configuration comparison program 40
determines a current configuration of the computer system, and
compares the current configuration of the computer system with the
reference configuration to determine whether the current
configuration differs from the reference configuration. The
configuration comparison program 40 may, for example, determine the
current configuration of the computer system in the same manner as
that described above with respect to the configuration capture
program 30.
[0028] The configuration comparison program 40 may, for example,
compare the current configuration of the computer system with a
reference configuration by retrieving the stored information
descriptive of the reference configuration from the configuration
file 32. The configuration comparison program 40 may detect, for
example, whether new devices are present, old devices have been
deleted, or existing devices have moved. When doing so, the
configuration comparison program 40 may examine the information for
both the current and reference configurations that identifies
devices in a manner that is not dependent upon the physical
configuration of the computer system (e.g., using the storage
system serial number and unique logical volume identifier discussed
above). Thus, the status of a device is not determined based on the
operating system device identifier which is dependent upon the
system configuration, but rather, is based upon information that
uniquely identifies the device in a manner that is independent of
the configuration of the system.
[0029] In one illustrative embodiment of the present invention, an
indication is provided by the configuration comparison program 40
when the current configuration of the computer system differs from
a reference configuration. For example, the configuration
comparison program may provide an indication when the channel
through which a particular logical volume is accessible has
changed, when a previously accessible logical volume is no longer
accessible, or when any other change to the configuration of the
computer system is detected.
[0030] The indication that the current configuration of the
computer system differs from the reference configuration may be
provided in any manner, and the present invention is not limited to
any particular technique. For example, a text file descriptive of
the differences between the current configuration of the computer
system and the reference configuration may be generated. The
indication may be provided to a human operator by, for example,
displaying such a text file on a computer monitor 42, printing the
text file on a printer 44, or sending the text file to a human
operator in an e-mail message via a modem 46. The human operator
may use the information contained within the indication provided by
the configuration comparison program 40 to determine what steps, if
any, to take in response to the changes in the computer system's
configuration to avoid system errors. The operator may, for
example, reconfigure the file system/LVM mapping layer 23 to refer
to devices using their new device identifiers.
[0031] In one embodiment of the invention, the configuration
comparison program 40 executes every time the host computer 1 is
rebooted, halts the rebooting of the host computer 1 when it is
determined that the current configuration of the computer system
differs from the reference configuration, and provides an
indication that the configuration of the system has changed. The
configuration comparison program 40 may then allow a human operator
to disregard the message and continue the bootup process.
[0032] The configuration comparison program 40 may be implemented
to provide an indication of all differences detected between the
current configuration of the computer system and the reference
configuration, or it may be implemented to provide an indication of
only certain types of differences. For example, in a computer
system that includes a number of system resources connected to a
host computer, in one embodiment of the present invention, the
configuration comparison program 40 only provides an indication of
differences impacting raw storage devices or logical volumes
included in a storage system 3.
[0033] The illustrative embodiments of the present invention
discussed above have been described in connection with an
illustrative system such as that shown in FIG. 4, wherein the
computer system includes a host computer 1 and a computer system
resource that is a storage system 3 such as that shown in FIG. 1.
However, it should be appreciated that the present invention is not
limited in this respect, and that the aspects of the present
invention described above can be used in connection with computer
systems having numerous other configurations, so that the host
computer 1 can determine system configuration changes in connection
with numerous system resources other than a storage system 3. In
addition, as described above, Fibre Channel has provided an
environment wherein system configuration changes have become more
prevalent, such that the embodiments of the present invention
discussed above can be advantageous when used in connection with a
Fibre Channel system. However, it should be appreciated that the
present invention is not limited in this respect, and can be used
in connection with numerous other system configurations that do not
employ the Fibre Channel protocol.
[0034] It should be understood that the present invention is not
limited to use with any particular computer platform, computer
processor, or high-level programming language. Although aspects of
the present invention are discussed above as being implemented in a
programmed processor, elements of the invention may be implemented
in software, hardware, firmware, or any combination thereof. The
various elements of the invention, either individually or in
combination, may be implemented as a computer program product
tangibly embodied in a machine-readable storage device for
execution by a computer processor such as the processor 16 shown in
FIG. 1. Various steps of embodiments of the invention, such as
those described above and illustrated using flow charts, may be
performed by a computer processor executing a program (i.e.,
software or firmware) tangibly embodied on a computer-readable
medium to perform functions by operating on input and generating
output. The computer-readable medium may be a memory in the host
computer 1 (FIG. 1), or a transportable medium such as a compact
disk, a floppy disk, or a diskette, such that a computer program
embodying the aspect of the present invention can be loaded onto
any computer. The computer program is not limited to any particular
embodiment and may, for example, include an application program,
foreground or background process, driver, or any combination
thereof, executing on a single computer processor or multiple
computer processors. Computer programming languages suitable for
implementing such a system include procedural programming
languages, object-oriented programming languages, and any
combination thereof.
[0035] Having described several embodiments of the invention in
detail, various modifications and improvement will readily occur to
those skilled in the art. Such modifications and improvements are
intended to be within the spirit and scope of the invention.
Accordingly, the foregoing description is by way of example only,
and is not intended as limiting. The invention is limited only as
defined by the following claims and the equivalents thereto.
[0036] What is claimed is:
* * * * *