Methods and systems for moving data objects

A method comprising selecting a data object from a first storage location; assigning an identifier (ID) to the data object; storing the ID in a transactional type lock object; determining whether the ID is stored successfully in the transactional type lock object, and upon a successful storage, storing the ID in a permanent type lock object; determining whether the ID is stored successfully in the permanent type lock object, and upon a successful storage, deleting the ID from the transactional type lock object; storing the data object at the second storage location; assigning the second storage location to the ID in the permanent type lock object; deleting the data object from the first storage location; and deleting the ID from the permanent type lock object after the respective data object assigned to that ID has been deleted from the first storage location.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The technical field of this invention is in the area of electronic data processing. More particularly, the invention relates to methods, computer program products and systems for data moving.

2. Description of the Related Art

Moving of data objects is well known to every user of a computer and is a standard procedure, which is routinely applied. A special application of moving data objects is the archiving process, by which data objects are moved from a first to a second storage location for safety and/or performance reasons. In enterprises, enterprise resource planning software (ERP) applications are used to control or support business processes and the management of the enterprise. ERP software is further used to manage company information of enterprises of various kinds in any field of technology by means of automatic data processing systems such as computers or computer systems. During the use of such software a huge amount of data is usually created, which contains important business information and which has to be archived from time to time.

According to the state of the art (see Helmut Stefani, Datenarchivierung mit SAP, Galileo Press GmbH, Bonn 2002, ISBN 3-89842-212-7), archiving can be performed automatically by archiving software tools, which can be part of the ERP software. Such tools can consist of a writing module, which stores (writes) the data objects to be archived sequentially in archive files, and a deleting module, which deletes the successfully archived data from the original data object base. The writing module can select the data objects to be archived from the data base according to specific criteria, e.g. the creation time of the data. It usually does not modify the original data objects or data base. The deleting module staggeredly reads the archive file sequentially and deletes the data objects found in the archive file from the original data base. This ensures that only such data objects are deleted from the original data base, which are readably stored in the archive file. The time for the archiving procedure as a whole depends on the amount of data and varies from a few milliseconds to several hours or days. Consequently, there is in many cases a considerable time gap between writing the data into the archive file and deleting the data from the original data base. This time gap can be a reason for the following problems:

As long as the data objects are still available in the original database, they can still be modified during the time gap. Because the deleting program does not compare the archived data object and the data object to be deleted, such modifications can be lost. This has not only the consequence of the loss of the amended data, it can additionally have the consequence that certain business processes can not be completed.

Another problem arises if several archiving processes run in parallel. In this scenario, that one data object can be archived several times, and is no longer unambiguously identifiable. This can have the consequence that evaluations or statistical analysis, which use the archive files, produce wrong results.

It is also possible that data objects in the original database are read by the writing module and are simultaneously modified by another software application. In such a case, the data can be transferred from an archiveable status to a non-archiveable status. As a result, data objects which are not archiveable are written into the archive file and are deleted from the original database. In effect, this can result in a loss of data.

Thus, there is a need for a method and/or data processing system providing a more efficient solution of the problems described above.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, as embodied and broadly described herein, methods and systems consistent with the principles of the invention provide for moving data objects in a computer system from a first storage location to a second storage location, comprising:selecting one or more data objects from the first storage location;assigning at least one identifier (ID) of at least one type to each of the selected data objects;storing the at least one ID in a lock object;storing a data object, the ID of which is contained in the lock object, at the second storage location and assigning the second storage location to the ID in the lock object;deleting the data object, the ID of which is contained in the lock object, from the first storage location; anddeleting the ID from the lock object after the step of deleting the data object from the first storage location for the respective data object assigned to that ID has been completed.

By using this method, software applications, which require access to data objects, can check by querying the lock object, whether the data to be accessed are subject to a moving process or not. If yes, the access to that data can be postponed until the moving is completed.

In accordance with another aspect of the invention, as embodied and broadly described herein, methods and systems consistent with the principles of the invention provide a computer system for processing data, comprising:memory means for storing program instructions;input means for entering data;storage means for storing data;a processor responsive to program instructions; andprogram instructions adapted to carry out the method described above.

The invention and its embodiments are further directed to a computer readable medium and a carrier signal comprising instructions for processing data according to the inventive method and in its embodiments.

One advantage of the invention and its embodiments is that the security against data loss in data moving and archiving procedures may be greatly improved. This may avoid spending a lot of time and money for data retrieval.

Additional objects and advantages of the invention and its embodiments will be set forth in part in the description, or can be learned by practice of the invention. Objects and advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. Embodiments of the invention are disclosed in the detailed description section and in the dependent and appended claims as well.

DETAILED DESCRIPTION

Computer systems and programs are closely related. As used hereinafter, phrases, such as “the computer provides” and “the program provides or performs specific actions,” and “a user performs a specific action” are convenient abbreviations to express actions by a computer system that is controlled by a program or to express that the program or program module is designed to enable the computer system to perform the specific action or the enable a user to perform the specific action by means of a computer system.

Reference will now be made in detail to the principles of the invention by explaining the invention on the basis of an archiving process, examples of which are illustrated in the accompanying drawings. Examples, mentioned therein, are intended to explain the invention and not to limit the invention in any kind.

Within the concept of this description, the terms used shall have their usual meaning in the context of the field of data processing unless defined otherwise in the following section:

A computer system can be a stand alone computer such as a PC or a laptop or a series of computers connected as a network, e.g. a network within a company, or a series of computers connected via the internet. A data object to be archived can be any kind or type of data, e.g. numerical or textual data, image data, meta data, irrespective whether the data are implemented as whole files or parts of files or fields in tables, irrespective whether they are stored in volatile memory or nonvolatile memory. As an example, data objects according to the present invention can be implemented as one or more fields of one or more tables, particularly of tables of a relational data base system, or as objects in an object orientated programming language.

The term ERP software shall be considerer to comprise any software application that supports the business processes of an enterprise.

A storage location is volatile or nonvolatile storage means accessible by the computer system. It can be any kind of computer storage means known to one of ordinary skill, e.g. RAM, magnetical or optical storage, such as floppy disk, hard disk, MO-Disk, CD-ROM, CD RW, DVD ROM, DVD RW, etc. The first and second storage location can be identical. In this case, the archived data objects have to be stored at a place different to the place of the original data objects to be archived. The second storage location can also be implemented as a file, located anywhere in the accessible nonvolatile storage means. Such file is subsequently referred to as archive file.

An identifier (ID) is a type of data, which allows an unambiguous identification of the data object to be archived. It can be implemented, for example, as a number or a combination of alphanumerical characters or as a characteristic part of the data object to be archived. It is clear from that definition that a data object can have a wide variety of IDs. A lock object is a data object, in which the identifiers are stored. It can be implemented, e.g., as a file on a storage means or as a data array in computer memory. A first lock object is stored advantageously in a nonvolatile storage means and a second lock object is stored in volatile and/or nonvolatile storage means.

The assignment of the second storage location to an ID can be implemented by a table, in which one field of a line contains the ID and another field of that line contains a link to the second storage location, e.g. a file name. This table can be stored as a file on a nonvolatile storage means.

FIG. 1is a schematic block diagram of an exemplary implementation of a computer system.FIG. 1shows a computer system101comprising a computer103having a CPU105, a working storage112, in which an ERP software111is stored for processing by CPU105. ERP software111comprises program modules106,109,110for carrying out the inventive data archiving process. Computer system101further comprises input means113, output means112for interaction with a user, and general input/output means104, including a net connection114, for sending and receiving data. A plurality of computer systems101can be connected via the net connection114in the form of a network113. In this case, the network computers113can be used as further input/output means, including as further storage locations. Computer system103further comprises a first storage means107, in which data to be archived and the lock object are stored, and a second storage means108, in which the archived data are stored.

In case the program modules106,109,110are processed by CPU105in order to carry out the inventive process, one or more data objects stored in the first storage means107are selected by selection module110. Selection module110assigns an ID to each of the selected data objects and stores the ID in the lock object at the storage location107. Writing module106reads the data objects and the lock object and stores such data objects, the ID of which are contained in the lock object to the second storage location108. Additionally, the second storage location108is assigned to the respective ID of the data object in the lock object. Deleting module109then reads the archived data objects in the second storage location108and deletes the data objects, which it could successfully read from the original set of data objects in the first storage location107. After deleting a specific data object, to which an ID was assigned, that ID is deleted from the lock object.

In an alternative embodiment, the lock object may be created by the selection module and not by the writing module.

In a second implementation of the invention, a data object to be archived may comprise of one or more fields of one or more tables, and the ID of the respective object may comprise of one or more key fields of that data object. This can best be seen fromFIG. 2. In this instance, various sets of data objects are created in the form of two-dimensional data arrays, i.e., two tables (table 1 and table 2) having columns named field A to field X and field A to field Y, respectively, and a certain, unspecified number of lines. A field of the array or table is defined by the name of the column and the respective line. Such a field can contain data to be archived. It can alternatively contain a reference to a line of a further table. For example, in table 1 field X in line2contains a reference to line3in table 2. A data object to be archived comprises of fields of one line of the respective table. If one of the fields contains a reference to a line of an other table, fields of this referenced line belong to the data object as well. In the example inFIG. 2, a data object to be archived comprises the fields of line2in table 1 and fields of line3in table 2.

An ID of such a data object can be implemented by the content of one or more so-called key fields, if the combination of these key fields is unique within the respective table. In the example, the fields of “held A” and “field B” can be used as key fields for table 1, whereas field A alone is key field in table 2. Within this example, assigning an ID to the data object means to use the content of the fields of columns field A and B of the respective lines as the ID for that particular line. In line with this assignment, the IDs for the data object to be archived are stored as a first type ID in a first type lock object named permanent lock object inFIG. 2and as a second type ID in a second type lock object named transactional lock object. The permanent lock object may be implemented as a table having two columns, the first of which contains the first type ID1. The second type ID, ID2, may be implemented as a one-dimensional data array stored in the working memory of the computer system. However, it can be implemented as a file on a nonvolatile storage means, too. The first type ID, ID1, is deleted after the selected data object has been deleted according to the inventive process, and the second type ID, ID2, may be deleted immediately after. Alternatively, type ID1IDs can be deleted after all the selected data objects have been deleted. As can be seen, both ID types have identical content, the ID of the respective lines of the data to be archived. However, this is not a necessary condition. It can be seen from the fact that the ID2of line BB is deleted, that this line has already been archived, whereas line BC has not yet been stored to the archive file. The two types can also be stored together in one lock object. The permanent lock objects further contain a column by which a filename may be assigned to the ID of the data object, i.e. that data object to be archived. In the example, line1is archived in a file named001, lines2and3in file002, and line4in file003.

The selection of the data object can be implemented by an automatic procedure, such as by a simple query, that returns all lines having a certain field that satisfies a certain condition. For example, the procedure could return all lines in which the content of a date field pre-dates or post-dates a certain deadline. Selection can also be implemented by a user to whom a selection table is presented via a graphical user interface.

A further embodiment may comprise storing the ID in a second lock object immediately after assigning at least one identifier (ID) of at least one type for the respective data object. Alternatively, the second type of ID of the selected data object is stored before storing the data object assigned to that ID is started.

A further embodiment may comprise storing the IDs of the first type of all selected data objects before storing the data object at the second storage location.

In a further embodiment, the invention may comprise checking whether an ID for that data object has been stored in a lock object, and if the ID has been stored, not storing the data object at the second location and assigning the second storage location to the ID in the lock object for that data object.

Additionally, the invention may comprise checking whether the data object is contained in the second storage location, and if the data object is contained, not storing the data object, the ID of which is contained in the lock object, at the second location and assigning the second storage location to the ID in the lock object for that data object.

Another embodiment may comprise checking by querying a lock object.

Another embodiment may comprise checking whether the data object assigned to the respective ID has been completely stored in the second location and, if the data object has not been stored, skipping the step of deleting the data object from the first storage location and the step of deleting the ID from the lock object after the respective data object assigned to that ID has been deleted for that data object and deleting the ID from the lock object.

Embodiments of the invention are now described in more detail with reference toFIGS. 3 to 5, which are schematic flow diagrams of exemplary methods that may be implemented by the selecting, writing and deleting modules, respectively, as shown inFIG. 1. Within the context of this description, and particularly with respect toFIGS. 3 to 9, a first type ID is called a P-lock (permanent) and a second type ID is called a T-lock (transactional). Therefore, setting a P or T-lock for a selected object means to store an ID of that object in a respective lock object. The term “permanent” results for the property of the P-lock of existing permanently, as long as the data object is not yet deleted from its original storage location. The term “transactional” results from the property of the T-lock of existing only as long as a specific action (e.g. checking of archiveability) is performed on a selected data object or, in other words, of being deleted after the respective action has been performed.

In the exemplary flow chart of the selecting module inFIG. 3, a data object is selected in a first step301. Subsequently, a T-lock is set on this object in step302. If the T-lock was successfully set (step303), that is, if it did not yet exist, it is checked in step304whether a P-lock already exists in the selected data object. If not, the next data object is selected in step309. The selling of the T-lock (step302) and the check (step303), whether it is successfully, set can advantageously be implemented as one “atomic” step. This means that both steps can be executed essentially at the same time or, in other words, the time gap between both can be essentially zero.

Both checks (steps303and304) can also be implemented by querying the respective lock objects. If a P-lock exists, the T-lock is deleted (step308) and the next data object is selected (step309). If no P-lock exists, it is checked in steps305and306whether the data object is archiveable. Such checking comprises a test of whether the data in the data object is readable, complete, or not fraught with obvious failures etc. If the test is successful, a P-lock is set on that data object in step307, whereby no archive file is assigned to the data object at that point. Then the T-lock is deleted (step308) and the next data object is selected (step309).

In the exemplary flow chart of the writing module inFIG. 4, a data object is selected in a first step401. Subsequently, a T-lock is set on this object in step402. If the T-lock was successfully set (step403), it is checked in step404whether a P-lock already exists in the selected data object, whereby no file must be assigned to that data object at that point of the process. If the condition is not fulfilled, the T-lock is deleted in step407, and the next data object is selected in step408. If a P-lock exists, the data object is stored in an archive file in step405and the archive file is assigned to the data object in step406, e.g., by adding the file name to the lock object as shown inFIG. 2. Subsequently, the T-lock is deleted (step407), and the next data object is selected (step408).

In the exemplary flow chart of the deleting module inFIG. 5, a data object that has already been archived is selected (step501). This can be implemented by checking the archive files. If a data object has been selected and successfully read from the archive file, that data object is deleted from the original storage location (step502), the P-lock is deleted (step503), and the next data object is selected (step504).

In the exemplary flow chart of a further exemplary implementation inFIG. 6, the selecting module and writing module described above are combined to one module. Accordingly, a data object is selected in a first step601. Subsequently, a T-lock is set on this object in step602. If the T-lock was successfully set (step603), it is checked in step604whether a P-lock already exists in the selected data object. If the T-lock could not be set successfully, the next data object is selected (step610). If a P-lock exists on that object, the T-lock is deleted (step609) and the next data object is selected (step610). If no P-lock exists on that object, it is checked in step605whether the data object is archiveable. If this check fails (step606), the T-lock is deleted (step609), and the next data object is selected (step610). If the check is positive, the data object is stored (step605) in an archive file, a P-lock is set (step608) with the archive file assigned, the T-lock is deleted (step609), and the next data object is selected (step610).

FIG. 7shows a flow chart of an exemplary method to demonstrate how any software application can use the concept of the P and T-locks to ensure that the measures, that the software application is going to apply on the data object do not influence the archiving process. A software application that is programmed to have a read and/or write access to data objects, which can be subject of an archiving process as described, may comprise the following steps as shown inFIG. 7. In a first step701, the data object is selected. Then a T-lock is set in step702on that object by the application. If the T-lock is successfully set (step703), it is checked in step704, whether a P-lock exists on that object; otherwise the application terminates in step707. If a P-lock exists on that object (step704), the T-lock is deleted (step706), and the application terminates (step707). If no P-lock exists, i.e., the data object is not subject to an archiving process, the application can have read/write access to the data object in a working step705. Subsequently, the application deletes the T-lock (step706) and terminates (step707).

FIG. 8is a flow chart of another exemplary method to demonstrate how any software application may use the concept of the P and T-locks, including a conditional deletion of a P-lock. In a first step801, the data object is selected. Then, a T-lock is set on that object by the application (step802). If the T-lock is successfully set (step803), it is checked (step804) whether a P-lock exists on that object; otherwise the application terminates (step809). If no P-lock exists (step804), i.e., the data object is not subject to an archiving process, the application can have read/write access to the data object in working step807. Subsequently, the application deletes the T-lock (step808) and terminates (step809). If a P-lock exists (step804), it is checked (step805) whether a file is assigned to it. If a file is assigned, the application deletes the T-lock (step808) and terminates (step809). If no file is assigned, the P-lock is deleted (step806), and the application can have read/write access to the data object (step807). Subsequently, the application deletes the T-lock (step808) and terminates (step809).

This procedure is particularly useful, in that data objects, which are not yet stored in an archive file, can be still altered. Consequently, they can be archived only at the next archive run.

FIG. 9is a flow chart of an exemplary method for implementation by a software module through which the locks set by the modules described above can be deleted. This can be useful in cases in which no archive files are assigned to P-locks or in which P-locks have been deleted for a user. Therein, a P-lock is nothing else than a data object and can be treated in the same way as described above. In a first step901, a P-lock is selected. Then, a T-lock is set to the P-lock in (step902). If the T-lock is successfully set (step903), it is checked (step904), whether the P-lock has a file assigned. If the T-lock is not set successfully, the module terminates (step907). If the selected P-lock has no file assigned (step904), the P-lock is deleted (step905). Then the T-lock is deleted (step906) and the module terminates (step907). Alternative to the termination step907, a next P-lock can be selected.

Modifications and adaptations of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The foregoing description of an implementation of the invention has been presented for purposes of illustration and description. It is not exhaustive and does not limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from the practicing of the invention. For example, the described implementation includes software, but systems and methods consistent with the present invention can be implemented as a combination of hardware and software or in hardware alone. Additionally, although aspects of the present invention are described for being stored in memory, one skilled in the art will appreciate that these aspects can also be stored on other types of computer-readable media, such as secondary storage devices, for example, hard disks, floppy disks, or CD-ROM; the Internet or other propagation medium; or other forms of RAM or ROM. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Computer programs based on the written description and flow charts of this invention are within the skill of an experienced developer. The various programs or program modules can be created using any of the techniques known to one skilled in the art or can be designed in connection with existing software. For example, programs or program modules can be designed in or by means of ® Java, C++, HTML, XML, or HTML with included Java applets or in SAP R/3 or ABAP.