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BACKGROUND OF THE INVENTION
This invention relates to a data recovery system for use in a data
processing or computer system which is used for carrying out data
processing in compliance with a transaction processing program on data
blocks memorized in a data file on a block by block basis.
Various data recovery systems are already known. The data recovery system
is used for recovering those of the data blocks which are damaged or
otherwise adversely affected in the data file due to a system failure or
system down. In other words, the data recovery system is used for carrying
out data recovery on the data blocks which should be recovered into
recovered blocks. For such a data recovery system, the data processing
system is operable in combination with the data file and a recovery log
file. The transaction processing program specifies data retrieval and data
renewal among others. The data processing system comprises a block memory
area, an activation controlling arrangement responsive to a first control
signal for controlling activation of the transaction processing program, a
block transferring arrangement for transferring data blocks during the
data retrieval from the data file to the block memory area for storage
therein as memorized blocks, a block retrieving arrangement for retrieving
during the data retrieval those of the memorized blocks from the block
memory area for data processing in compliance with the transaction
processing program which are specified by the transaction processing
program, a data updating or renewing arrangement for updating during the
data renewal those of the memorized blocks in the block memory area into
updated blocks which are specified by the transaction processing program,
and a log storing arrangement coupled to the data updating arrangement for
storing log data in the recovery log file upon renewal of the memorized
blocks in the block memory area into the updated blocks. The data recovery
system includes a log memory area, a log transferring arrangement for
transferring the log data from the recovery log file to the log memory
area, and a block storing arrangement for storing during the data renewal
and the data recovery the updated and the recovered blocks in the data
file from the block memory area. The data recovery is carried out on
restarting or rerunning the transaction processing program after
occurrence of the system failure.
In a conventional data recovery system, the transaction processing program
is again activated after completion of the data recovery. It is to be
noted in this connection that some of the data blocks need not be
recovered even for an occurrence of the system failure and can be
processed before completion of the data recovery of the data blocks which
must be recovered.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a data
recovery system wherein data recovery is carried out only on data blocks
which must be recovered.
It is another object of this invention to provide a data recovery system of
the type described, wherein a transaction processing program can at once
be restarted after occurrence of a system failure on data blocks which
need not be recovered.
It is still another object of this invention to provide a data recovery
system of the type described, whereby a data processing system is operable
at a high speed.
Other objects of this invention will become clear as the description
proceeds.
In describing the gist of this invention, it is possible to define that a
data recovery system is used in a data processing system which is operable
in combination with a data file and a recovery log file and in compliance
with a transaction processing program specifying data retrieval and data
renewal and comprises a block memory area into which data blocks are
transferred from the data file, activation controlling means responsive to
a first control signal for controlling activation of the transaction
processing program, block retrieving means for retrieving during the data
retrieval those of the data blocks from the block memory area for data
processing in compliance with the transaction processing program which are
specified by the transaction processing program, data updating means for
updating during the data renewal those of the data blocks in the block
memory area into updated blocks which are specified by the transaction
processing program, and log storing means coupled to the data updating
means for storing log data in the recovery log file upon renewal of data
blocks in the block memory area into the updated blocks. In order to carry
out data recovery of those of the data blocks in the block memory area
into recovered blocks which should be recovered, the above-defined data
recovery system includes a log memory area, log transferring means for
transferring the log data from the recovery log file to the log memory
area, and block storing means for storing during the data renewal and the
data recovery the updated and the recovered blocks in the data file from
the block memory area.
According to this invention, the afore-defined data recovery system
comprises information producing means coupled to the log memory area and
responsive to a second control signal for producing block-up information
indicative of each data block which should be recovered, first deferring
means coupled to the block retrieving means and the information producing
means for deferring retrieval of those of the data blocks which are
indicated by the block-up information as blocked-up blocks, second
deferring means coupled to the block storing means and the information
producing means for deferring storage of the blocked-up blocks in the data
file, and control signal producing means for producing the second control
signal upon carrying out the data recovery and thereafter the first
control signal to activate the transaction processing program on each data
block which is not one of the blocked-up blocks.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram of a data processing system which includes a data
recovery system according to an embodiment of the instant invention;
FIG. 2 is a detailed diagram of a recovery information memory area used in
the data recovery system shown in FIG. 1;
FIG. 3 is a flow chart for use in describing operation of a control signal
producing arrangement used in the data recovery system depicted in FIG. 1;
FIG. 4 is a flow chart for use in describing operation of a recovery
controlling unit used in the data recovery system illustrated in FIG. 1;
FIG. 5 is a flow chart for use in describing operation of an information
producing unit used in the data recovery system shown in FIG. 1;
FIG. 6 is a flow chart for use in describing operation of a data recovering
unit used in the data recovery system depicted in FIG. 1;
FIG. 7 is a flow chart for use in describing operation of a block
transferring arrangement used in the data processing system illustrated in
FIG. 1;
FIG. 8 is a flow chart for use in describing operation of a block storing
unit used in the data recovery system depicted in FIG. 1;
FIG. 9 is a flow chart for use in describing operation of a data retrieving
arrangement used in the data processing system shown in FIG. 1; and
FIG. 10 as a flow chart for use in describing operation of a data updating
arrangement used in the data processing system illustrated in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a data processing or computer system includes a data
recovery system according to a preferred embodiment of the present
invention. The data processing system is operable in combination with a
data file 21 for memorizing data blocks on a block by block basis as file
data blocks, a recovery log file 22, and a primary log file 23 and in
compliance with a transaction processing program 25 which is depicted as a
structural element of the data processing system merely for convenience of
illustration. The transaction processing program 25 specifies data
retrieval and data renewal besides data processing in the manner which
will presently become clear.
The data processing system comprises a block memory area 26 and a log
memory area 27. Responsive to a first control signal which will later be
described, an activation controlling arrangement 31 controls activation of
the transaction processing program 25. It is convenient depending on the
circumstances to regard the log memory area 27 as a structural element of
the data recovery system.
It will be now assumed that the transaction processing program 25 is
activated. Controlled by the transaction processing program 25 in the
manner known in the art, a block transferring arrangement 32 transfers
during the data retrieval those of the file data blocks from the data file
21 to the block memory area 26 which are specified by the transaction
processing program 25 as specified data blocks. Also during the data
retrieval, a data retrieving arrangement 33 supplies the transaction
processing program 25 with each datum which is selected from the specified
data blocks by the transaction processing program 25. Such data of the
specified data blocks are data processed in compliance with the
transaction processing program 25 into processed data. Operation of the
data transferring and the data retrieving arrangements 32 and 33 will be
described more in detail in the following.
During the data renewal, a data updating or renewing arrangement 34
substitutes the processed data on the block by block basis as processed
data blocks in the block memory area 26 for those of the specified data
blocks which are found in the meantime to be out of date in the known
manner and are called before images in the art. In other words, the data
updating arrangement 34 updates those of the data blocks in the block
memory area 26 which are specified by the transaction processing program
25. In this manner, the block memory area 26 memorizes various data blocks
as memorized data blocks. During progress of the transaction processing
program 25, some of the memorized data blocks are the specified data
blocks. Some others of the memorized data blocks are the processed data
blocks. Operation of the data updating arrangement 34 will later be
described more in detail.
A log storing arrangement 35 is coupled to the data updating arrangement
34. Whenever the memorized data blocks are updated in the block memory
area 26, the log storing arrangement 35 stores a data renewal log datum in
the primary log file 23 as one of log data. In the manner which will
become clear as the description proceeds, the log storing arrangement 35
stores various other log data in the primary log file 23. Such log data
are transferred from the primary log file 23 to the recovery log file 22
in the manner known in the art and are memorized in the recovery log file
22 as file log data. It is therefore possible to understand that the log
storing arrangement 35 serves to store the file log data in the recovery
log file 22.
When the data processing system is subjected to a system failure or system
down, operation of the transaction processing program 25 is suspended. The
data recovery system is put into operation of carrying out data recovery
for those of the file data blocks which should be recovered to the before
images. In other words, the data recovery system recovers some of the data
blocks in the block memory area 26 into recovered data blocks.
In order to carry out the data recovery, the data recovery system includes
a log transferring arrangement 36 for transferring the file log data from
the recovery log file 22 to the log memory area 27. The file log data are
successively stored in the log memory area 27 as memorized log data in
this manner.
Responsive to the memorized log data, a recovery controlling unit 37
controls a data recovering unit 38 and a block storing unit 39. Into the
recovered data blocks, the data recovering unit 38 is controlled to
recover those of the processed data blocks which are damaged or otherwise
adversely affected by the system failure. The recovered data blocks are
stored in the block memory area 26 as the memorized data blocks in
addition to the specified data blocks and those of the processed data
blocks which need not be recovered. The block storing unit 39 is
controlled to transfer the updated and the recovered data blocks from the
block memory area 26 to the data file 21. In this manner, the block
storing unit 39 stores the updated and the recovered data blocks in the
data file 21. It is now understood that a combination of the recovery
controlling unit 37, the data recovering unit 38, and the block storing
unit 39 serves as a block storing arrangement coupled to the log memory
area 27 for storing during the data renewal and the data recovery the
updated and the recovered data blocks in the data file 22. Operation of
the recovery controlling, the data recovering, and the block storing units
37 through 39 will be described in greater detail in the following.
In the example being illustrated, the data recovery system comprises a
recovery information memory area 41 and a block-up information memory area
42. Coupled to the log memory area 27 and responsive to a second control
signal which will presently be described, an information producing unit 43
produces block-up information indicative of each memorized data block
which should be recovered in the block memory area 26. Among the memorized
data blocks, those indicated by the block-up information are herein
referred to as blocked-up data blocks. The block-up information is stored
in the block-up information memory area 42. Controlled by the recovery
controlling unit 37, a control signal producing arrangement 45 produces
the first and the second control signals and other control signals which
will shortly be described. Operation of the information producing unit 43
and the control signal producing arrangement 45 will be described in
detail hereunder.
Turning to FIG. 2 for a short while, the recovery information memory area
41 has recovery progress and completion flag fields 46 and 47 and a
recovery start log address field 48. In the manner which will become clear
as the description proceeds, the recovery progress flag field 46 is for a
recovery progress flag. The recovery completion flag field 47 is for a
recovery completion flag. The recovery start log address field 48 is for a
recovery start log address of the recovery log file 22 which is described
above in conjuction with FIG. 1.
Further turning to FIG. 3, operation of the control signal producing
arrangement 45 will be described. In the manner which will become clear as
the description proceeds, operation of some structural elements proceeds
in parallel.
Whenever the recovery controlling unit 37 detects necessity of the data
recovery in the manner known in the art, the control signal producing
arrangement 45 is put into operation and delivers the second control
signal at first to the information producing unit 43 at a first step A1.
When operation of the information producing unit 43 comes to an end, the
control signal producing arrangement 45 delivers a third control signal to
the log storing arrangement 35 at a second step A2 and then the first
control signal to the activation controlling arrangement 31 at a third
step A3. Operation of the transaction processing program 25, once
suspended upon occurrence of the system failure, is again activated by the
first control signal.
Having again activated operation of the transaction processing program 25,
the control signal producing arrangement 45 delivers a fourth control
signal back to the recovery controlling unit 37 at a fourth step A4 to
again put the recovery controlling unit 37 into operation.
Upon completion of the data recovery, the control signal producing
arrangement 45 delivers a fifth control signal to the log storing
arrangement 35 at a fifth step A5. Immediately thereafter, the control
signal producing arrangement 45 produces a sixth control signal at a sixth
step A6. Operation of the control signal producing arrangement 45 comes to
an end.
The sixth control signal is termed a releasing signal heretobefore. The
first through the sixth steps A1 to A6 will be called A1 through A6 steps
in the following.
It is to be noted in conjunction with FIGS. 1 and 3 that the log storing
arrangement 35 is operable during progress of the transaction processing
program 25. When a system failure takes place, the log storing arrangement
35 stores a recovery start log datum in the primary log file 23. Operation
of the transaction processing program 25 is suspended. The control signal
producing arrangement 45 produces the second control signal at the A1 step
to put the information producing unit 43 into operation at first during
the data recovery. After the block-up information is produced for all the
data blocks which should be recovered into the recovered data blocks, the
log storing arrangement 35 is put into operation by the third control
signal produced at the A2 step. The log storing arrangement 35 is now
capable of storing the data renewal log data in the primary log file 23
after the transaction processing program 25 is restarted by the first
control signal produced at the A3 step. When operation of the transaction
processing program 25 comes to an end, the log storing arrangement 35
stores a transaction end log datum in the primary log file 23. When the
data recovery comes to an end, the fifth control signal is produced at the
A5 step to make the log storing arrangement 35 store a recovery completion
log datum in the primary log file 23.
Turning back to FIG. 1, the releasing signal is supplied to a block-up
releasing unit 49. Activated by the releasing signal, the block-up
releasing unit 49 deletes the block-up information from the block-up
information memory area 42. It should be noted that the block-up
information is delivered from the block-up information memory area 42 to
the block transferring arrangement 32 and to the block storing unit 49
through first and second connections 51 and 52. As will later become
clear, the first and the second connections 51 and 52 serve as first and
second deferring arrangements.
Referring now to FIG. 4, the description will proceed to operation of the
recovery controlling unit 37 illustrated in connection with FIG. 1. In the
example being illustrated, the recovery controlling unit 37 is put into
operation by the fourth control signal which is produced by the control
signal producing arrangement 45 at the A4 step after operation of the
information producing unit 43 comes to an end and while the transaction
processing program 25 is in progress. It may be mentioned here that the
file log data are memorized in the recovery log file 22 time sequentially
in consecutive addresses for the data processing system being illustrated.
Put into operation, the recovery controlling unit 37 indicates at a B1 step
recovery start log address which is decided by the information producing
unit 43 and from which the consecutive addresses of the recovery log file
22 should be checked backwardly time sequentially. Immediately thereafter,
the recovery controlling unit 37 initializes the recovery information
memory area 41 at a B2 step. Next, the recovery controlling unit 37
delivers a first activation signal at a B3 step to the log transferring
arrangement 36 through a connection which is not depicted in FIG. 1 merely
for simplicity of illustration. Activated by the first activation signal,
the log transferring arrangement 36 loads the log memory area 27 with one
of the file log data that is memorized in the recovery log file 22 as a
recovery begin log datum at the recovery start log address.
The recovery begin log datum will be none of the data renewal log data and
the recovery completion log datum. Under the circumstances, the recovery
controlling unit 37 skips a loop consisting of B4 and B5 steps. The
recovery begin log datum may be the recovery start log datum. In this
event, the recovery controlling unit 37 confirms at a B6 step that the
recovery start log datum is transferred to the log memory area 27.
It is to be noted in this connection that the recovery completion log datum
will eventually be detected at the B4 step. The B5 step follows at which
the recovery completion flag is switched on in the recovery completion
flag field 47. At a B7 step, it is detected that the recovery completion
flag is on due to completion of the data recovery for the system failure
that took place next previous to the system failure being considered. The
B7 step returns to the B3 step without proceeding to a B8 step of
switching the recovery progress flag on in the recovery progress flag
field 46 and of storing the recovery start log address in the recovery
start log address field 48. The log transferring arrangement 36 is again
activated to transfer a next previous log datum to the log memory area 27.
Unless the log transferring arrangement 36 transfers one of the data
renewal log data to the log memory area 27, the recovery controlling unit
37 skips another loop consisting of B9 and B10 steps. At a B11 step, the
recovery controlling unit 37 confirms the fact that the transaction end
log datum is not yet transferred to the log memory area 27. This shows
that the data recovery is not yet complete. The B11 step returns to the B3
step. In this manner, the log transferring arrangement 36 is repeatedly
activated to read the recovery log file 22 from the recovery start log
address revesedly along the consecutive addresses.
Each time when the recovery controlling unit 37 finds at the B9 step that
the data renewal log data are transferred to the log memory area 27, the
recovery controlling unit 37 delivers a second activation signal at the
B10 step to the data recovering unit 38. In this manner, the recovery
controlling unit 37 controls the data recovering unit 38. When operation
of the data recovering unit 38 comes to an end in the manner which will
later be described in detail, the B10 step returns to the B3 step.
When the transaction end log datum is found at the B11 step, the recovery
controlling unit 47 knows completion of the data recovery. The B11 step
proceeds to a B12 step. The recovery progress flag is not turned on
because the B8 step is not carried out. As a consequence, the B12 step
does not proceed to a B13 step but proceeds to a B14 step of delivering a
third activation signal to the block storing unit 39. Controlling the
block storing unit 39 in this manner, operation of the recovery
controlling unit 37 comes to an end.
Referring to FIG. 5, operation of the information producing unit 43 will be
described. Put into operation by the second control signal produced by the
control signal producing arrangement 45 at the A1 step, the information
producing unit 43 initializes the block-up information memory area 42 at a
C1 step. Immediately thereafter, the information producing unit 43 decides
at a C2 step the recovery start log address which is presently used in
providing the recovery begin log datum of the type described in
conjunction with FIG. 4 and is later used by the recovery controlling unit
37 at the B1 step.
Like the recovery controlling unit 37, the information producing unit 43
subsequently initializes the recovery information memory area 41 at a C3
step and then supplies at a C4 step the log transferring arrangement 36
with an activation signal which is equivalent to the first activation
signal produced at the B3 step. Inasmuch as the recovery begin log datum
is not the recovery completion log datum, the information producing unit
43 skips a loop consisting of C5 and C6 steps which are similar to the B4
and the B5 steps.
At a C7 step, the information producing unit 43 finds the recovery start
log datum. The C7 step proceeds to a C8 step at which the information
producing unit 43 checks the recovery completion flag field 47. Inasmuch
as the recovery completion flag was switched on as a result of next
previous occurrence of a system failure, the C8 step returns to the C4
step of again activating the log transferring arrangement 36. It is to be
noted that a C9 step is not carried out in this event. Like the B8 step
described above, the C9 step is for turning the recovery progress flag on
in the recovery progress flag field 46 and for storing the recovery start
log address in the recovery start log address field 48.
Unless the data renewal log data are transferred by the log transferring
arrangement 36 to the log memory area 27, the information producing unit
43 skips another loop consisting of C10, C11, and C12 steps. The
transaction end log datum would neither be transferred to the log memory
area 27. Knowing at a C13 step that the data recovery is not yet complete,
the information producing unit 43 again carries out the C4 step. The log
transferring arrangement 36 is repeatedly activated.
When the information producing unit 43 finds at the C10 step that one of
the data renewal log data is transferred by the log transferring
arrangement 36 to the log memory area 27, the information producing unit
43 checks at the C11 step whether or not block-up information is already
memorized in the block-up information memory area 42 for the data block
which corresponds to the data renewal log datum under consideration. If
the block-up information is already memorized in the block-up information
memory area 42, the C11 step returns to the C4 step. If the block-up
information is not yet memorized in the block-up information memory area
42, the information producing unit 43 afresh stores block-up information
at the C12 step in the block-up information memory area 42 and then
returns to the C4 step. The information producing unit 43 produces the
block-up information in this manner.
When the information producing unit 43 eventually finds at the C5 step that
the recovery completion log datum is transferred to the log memory area
27, the C5 step proceeds to the C6 step of turning the recovery completion
flag on in the recovery completion flag field 47. The C5 step returns to
the C4 step and thence proceeds to the C5, the C7, and the C10 steps. At
the C13 step, the information producing unit 43 knows that the data
recovery is already complete. The C13 step proceeds to a C14 step of
checking the recovery progress flag field 46. Inasmuch as the C9 step is
not carried out, the recovery progress flag is off. As a result, the C14
step does not proceed to a C15 step. Instead, operation of the information
producing unit 43 comes to an end.
Turning to FIG. 6, operation of the data recovering unit 38 will be
described. Put into operation by the second activation signal produced by
the recovery controlling unit 37 at the B10 step, the data recovering unit
38 refers at a D1 step to the block and the log memory areas 26 and 27.
When no data block is found at the D1 step in the block memory area 26 in
correspondence to each log datum memorized in the log memory area 27, a D2
step is carried out to deliver a discrimination signal to the block
transfer arrangement 32. The discrimination signal indicates whether or
not the data recovery is carried out by the data recovering unit 38. When
the block memory area 26 memorizes a data block in correspondence to a log
datum memorized in the log memory area 27, the data recovering unit 38
proceeds to a D3 step of substituting a before image in the block memory
area 26 in the manner known in the art for the data block which
corresponds to the log datum in question. Operation of the data recovering
unit 38 comes to an end. In FIG. 4, the B10 step returns to the B3 step.
Referring now to FIG. 7, operation of the block transferring arrangement 32
will be described. The block transferring arrangement 32 is put into
operation on carrying out the data retrieval when the data retrieving
arrangement 33 is activated by the transaction processing program 25 in
the manner which will shortly be described. The block transferring
arrangement 32 is operable also during the data renewal specified by the
transaction processing program 25. In the manner indicated at an E1 step,
the operation proceeds to E2 and E3 steps when the discrimination signal
is not produced by the data recovering unit 38 at the D2 step, namely,
when the data retrieval is carried out rather than the data renewal. At
the E2 step, the block transferring arrangement 32 refers to the block-up
information memory area 42. At the E3 step, the block transferring
arrangement 32 checks whether or not the block-up information is memorized
in the block-up information memory area 42. If the block-up information is
memorized, a block transfer error code is produced at an E4 step. The
block transfer error code indicates blockade of a data block which should
otherwise be transferred from the data file 21 to the block memory area
26. Operation of the block transferring arrangement 32 comes to an end. If
the block-up information is not memorized, an E5 step is carried out to
transfer the data block from the data file 21 to the block memory area 26.
The operation comes to an end.
When the discrimination signal is delivered from the data recovering unit
38, namely, when the data renewal is carried out, the E1 step proceeds
directly to the E5 step. The operation comes to an end. Each time when
operation of the block transferring arrangement 32 comes to an end, the
data retrieving arrangement 33 is again put into operation during the data
retrieval in the manner which will presently be described.
Turning to FIG. 8, operation of the block storing unit 39 will be
described. The block storing unit 39 is put into operation during the data
renewal when the data updating arrangement 34 is activated by the
transaction processing program 25. In the manner indicated at an F1 step,
the operation proceeds to F2 and F3 steps while the recovery controlling
unit 37 does not produce the second activation signal at the B10 step,
namely, while the data recovery is not carried out. At the F2 step, the
block storing unit 39 refers to the block-up information memory area 42.
At the F3 step, the block storing unit 39 checks presence or absence of
block-up information in the block-up information memory area 42. Detecting
the presence, the block storing unit 39 produces a block storage error
code at an F4 step. The block storage error code indicates blockade of a
data block which should otherwise be stored in the data file 21 from the
block memory area 26. If no block-up information is present, an F5 step is
carried out to store the data block of the block memory area 26 in the
data file 21. In either event, operation of the block storing unit 39
comes to an end. The data updating arrangement 34 is again put into
operation during the data renewal as will presently be described.
When the second activation signal is detected at the F1 step, the F1 step
proceeds directly to the F5 step. Operation of the block storing unit 39
comes to an end to again put the data updating arrangement 34 into
operation.
Referring to FIG. 9, operation of the data retrieving arrangement 33 will
now be described. Put into operation by the transaction processing program
25 during the data retrieval, the data retrieving arrangement 33 supplies
at a G1 step the block transferring arrangement 32 with a first enable
signal to put the block transferring arrangement 32 into operation in the
manner described above with reference to FIG. 7. If produced by the block
transferring arrangement 32 at the E4 step, the block transfer error code
is sent to the data retrieving arrangement 33. When operation of the block
transferring arrangement 32 comes to an end, the data retrieving
arrangement 33 checks at a G2 step presence or absence of the data
transfer error code. If present, the block transfer error code is sent
back to the transaction processing program 25 at a G3 step. Operation of
the data retrieving arrangement 33 comes to an end. The transaction
processing program 25 proceeds so as again to carry out the data
retrieval.
When the block transfer error code is absent, the datum or data of the data
block are sent from the block memory area 26 to the transaction processing
program 25 at a G4 step. Operation of the data retrieving arrangement 33
comes to an end. The transaction processing program 25 carries out the
data processing on the datum or data.
Turning to FIG. 10, operation of the data updating arrangement 34 will be
described. Put into operation by the transaction processing program 25
during the data renewal, the data updating arrangement 34 stores at an H1
step the processed datum or data in the block memory area 26 on the block
by block basis as the processed data block. Next, the data updating
arrangement 34 supplies at an H2 step the block storing unit 39 with a
second enable signal to put the block storing unit 39 into operation. When
operation of the block storing unit 39 comes to an end, the data updating
arrangement 34 checks at an H3 step presence or absence of the block
storage error code produced by the block storing unit 39 at the F4 step.
If present, the block storage error code is sent at an H4 step to the
transaction processing program 25. Operation of the data updating
arrangement 34 comes to an end. The transaction processing program 25
proceeds so as to carry out the data retrieval for a next datum of the
data block memorized in the block memory area 26.
If the block storage error code is absent, the data updating arrangement 34
activates the log storing arrangement 35 at an H5 step. Activated, the log
storing arrangement 35 loads the primary log file 23 with a data renewal
log datum. After this operation of the log storing arrangement 35, the
data updating arrangement 34 informs the transaction processing program 25
of an end of operation of the data updating arrangement 34. The
transaction processing program 25 proceeds to the data retrieval for
another datum of the memorized data block.
Reviewing FIGS. 1 through 10, it is now understood that a combination of
the block-up information memory area 42, the information producing unit
43, and the block-up releasing unit 49 serves in cooperation with the
recovery information memory area 41 as an information producing
arrangement which is coupled to the log memory area 27 and responsive to
the second control signal for producing block-up information indicative of
each data block which should be recovered. When the block-up information
is produced for a data block, that data block is prevented from being
transferred from the data file 21 to the block memory area 26 in the
manner described in conjuction with the E4 step, being retrieved from the
block memory area 26 for supply to the transaction processing program 25
as described in connection with the G3 step, being stored from the block
memory area 26 in the data file 21 in the manner pointed out in
conjunction with the F4 step, and being updated in the block memory area
26 as described in connection with the H4 step.
In addition, the information producing unit 43 serves in cooperation with
the recovery information memory area 41 as an information storing
arrangement responsive to the second control signal for storing the
block-up information in the block-up information memory area 42 for each
data block which should be recovered. The block-up releasing unit 49
serves as an information deleting arrangement responsive to the releasing
signal for deleting the block-up information from the block-up information
memory area 42. The data retrieving arrangement 35 may alternatively be
called a block retrieving arrangement. The recovery controlling unit 37 is
activated by the fourth control signal in order to deal with the recovery
completion log datum which is stored in the primary log file 23 in
response to the fifth control signal.
It should furthermore be understood that the first connection 51 is coupled
to the information producing arrangement and to the block retrieving
arrangement through the block transferring arrangement 32. The first
connection serves to defer retrieval of the blocked-up data blocks from
the block memory area 26 until completion of the data recovery. The second
connection 52 is coupled to the block storing arrangement described
earlier and to the information producing arrangement to defer storage of
the blocked-up data blocks in the data file 21 until completion of the
data recovery. From a different view, it is possible to appreciate that
the first and the second deferring arrangements are first and second
classifying arrangements. During the data retrieval, the first classifying
arrangement classifies the data blocks of the block memory area 26 into
first and second groups. The data block or blocks of the first group must
be retrieved after the data recovery. The data block or blocks of the
second group can be subjected to the transaction processing program 25 at
once without waiting completion of the data recovery. During the data
renewal, the second classifying arrangement classifies the data blocks of
the block memory area 26 into third and fourth groups. The data block or
blocks of the third group must be stored in the data file 21 after the
data recovery. The data block or blocks of the fourth group can be stored
in the data file 21 at once without waiting completion of the data
recovery.
It is to be noted in connection with FIGS. 1 through 10 that an additional
system failure may take place during the data recovery. The system failure
described heretobefore, will be named a main system failure for
discrimination from the additional system failure. The data recovery
system detects the additional system failure like the main system failure.
As described earlier in conjuction with FIG. 3, the log storing arrangement
35 is activated by the third control signal produced by the control signal
producing arrangement 45 at the A2 step. When the additional system
failure takes place, the log storing arrangement 35 stores another
recovery start log datum in the primary log file 23. After the first
control signal is produced by the control signal producing arrangement 45
at the A3 step to again activate the transaction processing program 25,
the fourth control signal is produced at the A4 step to again activate the
recovery controlling unit 37 for processing of the additional system
failure. The recovery start log datum produced upon occurrence of the
additional system failure, will be called an additional recovery start log
datum.
In FIG. 5, the information producing unit 43 is already put into operation
by the second control signal produced by the control signal producing
arrangement 45 at the A1 step. At the C7 step, the information producing
unit 43 will detect a recovery start log datum. It should be noted that
the recovery completion flag would be kept off in the recovery completion
flag field 47 when the additional system failure takes place during the
data recovery. In this event, the recovery start log datum under
consideration is the additional recovery start log datum. The C8 step
therefore proceeds to the C9 step of turning the recovery progress flag on
in the recovery progress flag field 46 and of storing the recovery start
log address in the recovery start log address field 48 for the main system
failure. The C9 step returns to the C4 step of again activating the log
transferring arrangement 36. It is now understood that the recovery
progress flag is switched on each time when a system failure takes place
during progress of the data recovery.
Also in FIG. 5, the information producing unit 43 will eventually know
completion of the data recovery by finding a transaction end log datum at
the C13 step. This, however, is not true completion of the data recovery
because the information producing unit 43 detects at the C14 step that the
recovery progress flag is on in the recovery progress flag field 46. The
C15 step is therefore carried out at which the information producing unit
43 uses the reco | | |
