FIELD 
     Embodiments of the present invention relate to a technique for icon-displaying a file deletion and update history recorded in storage as additional data. More particularly, embodiments of the invention relate to a rollback function of a linear tape file system (LTFS) in a tape storage medium. 
     DESCRIPTION OF THE RELATED ART 
     There is a system, called LTFS, which uses a tape storage medium via a file system. In LTFS, a file itself is recorded on a tape medium as well as metadata, called an index, related to the recorded file, such as a file name, is also recorded on the tape medium. The process of recording an index on a tape medium is called sync. Thus, each of the indexes and each of the files are additionally and synchronously recorded as additional data, on the tape storage medium. In consequence, a history of the files is related to a plurality of indexes. The timing of sync can be set by a user, but a default sync may be every five minutes. 
     In LTFS, a file written to the tape medium remains recorded thereon until the tape medium is formatted again. In other words, even if a file recorded on a formatted tape medium is updated or deleted in LTFS, a yet-to-be updated file or a deleted file can be accessed by rolling back to an index written by past sync. The process of going back to a past index is called rollback. Currently, the amount of a history of indexes can be known, but it is challenging to understand the amount of an update history of files on a tape medium and the time of deletion of a deleted file. 
     It is impractical to require a user to make rollback to all the indexes recorded on a tape medium to check the metadata of the recorded file related to each index. A visual approach with a graphical user interface (GUI) is effective for a user in this respect. 
     SUMMARY 
     Since it is impractical to require a user to make rollback to all the indexes recorded on a tape medium to check the metadata of the recorded file related to each index, what is needed is a visual approach with a graphical user interface (GUI) to effectively inform the user of modifications of data within a file. 
     These and other embodiments, features, aspects, and advantages will become better understood with reference to the following description, appended claims, and accompanying drawings. 
     In an embodiment, a method of displaying icons on a display includes receiving a request for displaying an icon corresponding to a file recorded upon a storage medium, referring to a first index recorded upon the storage medium, determining whether, for the first index, data exists in the file corresponding to the received request, and displaying a first icon if the data exists. 
     Displaying the first icon may further include determining whether the first icon is displayed on the display, if the first icon is displayed, determining whether the data that exists in the file is updated, and if the data that exists in the file is updated, displaying overlapping the first icon an overlapping icon to indicate the data is updated. 
     Displaying the first icon may further include determining whether the first icon is displayed on the display, if the first icon is displayed, determining whether the data that exists in the file is updated, and if the data is updated, displaying an colored section having an first color within the first icon indicating the data is updated. 
     Displaying the first icon may further include determining whether the first icon is displayed on the display, if the first icon is displayed, determining whether the data that exists in the file is updated, and if the data is updated, deforming the first icon in a first deformation direction indicating the data is updated. 
     In other embodiments, one or more of the methods may be performed by a processor executing program instructions stored upon a non-transitory computer program product. For example, an LTFS may perform one or more of the methods to display an icon on a display. 
     In another embodiment, icons are represented on a display by computer execution of program instructions recorded upon a storage medium. The icons correspond to a history of files related to a plurality of indexes and each of the plurality of indexes and each of the plurality of files are additionally and synchronously recorded upon the storage medium. The icons represent a status of data in the files in the storage. 
     If no data exists in a file, a first icon may be displayed and a section is displayed within the first icon to indicate data was deleted. If data exists in the file and has been updated, an overlapping icon may be displayed overlapping the first icon to indicate the data is updated. An associated number of overlapping icons may be displayed each overlapping respective overlapping icons to depict the number of instances the files was updated. In certain embodiments, associated metadata is capable of being referred to by a user (e.g. GUI user) clicking an overlapping icon. 
     Alternatively, if no data exists in the file, the first icon may be displayed and a first section having a first color may be displayed within the first icon to indicate the data was deleted. If data exists in the file and has been updated, a section having a second color may be displayed within the first icon to indicate the data was updated. In embodiments, associated metadata is capable of being referred to by the user by clicking a different colored section of the first icon. 
     Alternatively, if no data exists in the file, the first icon may be displayed deformed in a first deformation direction to indicate the data was deleted. If data exists in the file and has been updated, the first icon may be displayed deformed in a second direction to indicate the data was updated. In embodiments, associated metadata is capable of being referred to by the user by clicking an extended or deformed section or part of the icon. 
     In certain embodiments, the user clicking a part of the first icon leads to rollback in a tape storage medium, the clicking being to access a yet-to-be updated file and to access a deleted file. 
     In another embodiment, a system displays the first icon upon a display, the system being configured to receive the request for displaying an icon corresponding to the file recorded upon the storage medium, refer to the first index recorded upon the storage medium, determine whether, for the first index, data exists in the file corresponding to the received request, and display the first icon if the data exists. 
     The system may be further configured to determine whether the first icon is displayed on the display, if the first icon is displayed, determine whether the data that exists in the file is updated, and if the data that exists in the file is updated, display overlapping the first icon an overlapping icon to indicate the data is updated. 
     The system may be further configured to determine whether the first icon is displayed on the display, if the first icon is displayed, determine whether the data that exists in the file is updated, and if the data is updated, display an colored section having an first color within the first icon indicating the data is updated. 
     The system may be further configured to determine whether the first icon is displayed on the display, if the first icon is displayed, determine whether the data that exists in the file is updated, and if the data is updated, deform the first icon in a first deformation direction indicating the data is updated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
       It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  illustrates an example of an icon of a file in accordance with embodiments of the present invention. 
         FIG. 2  illustrates an example of an icon of a file recorded on a tape medium and updated three times in accordance with embodiments of the present invention. 
         FIG. 3  illustrates an example of an icon of a file recorded on a tape medium, updated three times, and then deleted in accordance with embodiments of the present invention. 
         FIG. 4  is a flow chart of an exemplary method of displaying an icon in accordance with embodiments of the present invention. 
         FIG. 5  illustrates an example of an icon of a file recorded on a tape medium, updated three times, rolled back, and then updated twice again from an once updated file in accordance with embodiments of the present invention. 
         FIG. 6  illustrates an example of an icon of a file recorded on a tape medium and updated three times in accordance with embodiments of the present invention. 
         FIG. 7  illustrates an example of an icon of a file recorded on a tape medium, updated three times, and then deleted in accordance with embodiments of the present invention. 
         FIG. 8  is a flow chart of an exemplary method of displaying an icon in accordance with embodiments of the present invention. 
         FIG. 9  illustrates an example of an icon of a file recorded on a tape medium, updated three times, rolled back, and then updated twice again from an once updated file in accordance with embodiments of the present invention. 
         FIG. 10  illustrates an example of an icon of a file recorded on a tape medium and updated three times, the icon being four times as wide as a conventional icon, in accordance with embodiment of the present invention. 
         FIG. 11  illustrates an example of an icon of a file recorded on a tape medium, updated three times, and then deleted in accordance with embodiments of the present invention; 
         FIG. 12  is a flow chart of an exemplary method of displaying an icon in accordance with embodiments of the present invention. 
         FIG. 13  illustrates an example of an icon of a file recorded on a tape medium, updated three times, rolled back, and then updated twice again from an once updated file in accordance with embodiments of the present invention. 
     
    
    
     The drawings are not necessarily to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only exemplary embodiments of the invention. In the drawings, like numbering represents like elements. 
     DETAILED DESCRIPTION 
     It is an object of one or more embodiments to provide an icon for denoting a file history recorded on storage as additional data. More specifically, the icon is provided to facilitate visual understanding the amount or extent of an associated file&#39;s update history stored upon a tape storage medium and/or the time that which the file was deleted. 
     In an embodiment, when files recorded on a tape medium in the LTFS format are denoted via a GUI, icon symbols are overlapped depending on the number of updates to enable a user to readily understand the number of updates of files and execute rollback to each file by clicking any overlapped icon symbol. 
     In another embodiment, when files recorded on a tape medium in the LTFS format are denoted via a GUI, colors are added to an icon depending on the number of updates to enable a user to readily understand the number of updates of files and execute rollback to each file by clicking any different-color part of an icon. 
     In another embodiment, when files recorded on a tape medium in the LTFS format are denoted via a GUI, an icon is extended depending on the number of updates to enable a user to readily understand the number of updates and execute rollback of each file by clicking any deformed (e.g., extended in a width direction) part of an icon. 
     In yet another embodiment, the icon can be readily viewed in its entirety, which enables a user to refer to the metadata of each file recorded on a tape medium, allows for rollback to any of the indexes, and obviates the need for scrutinizing the metadata of the recorded file at each index. Rollback to each file may be enabled by clicking an overlapped icon, a different-color part of an icon, a deformed part of an icon, etc. 
     A file that is recorded on a tape storage medium and remains not updated is denoted by an icon as illustrated in  FIG. 1 . A file that is recorded on a tape medium and then updated may be denoted by an icon having symbols overlapped. For example, if the file is updated three instances, the icon includes four overlapping symbols, as illustrated in  FIG. 2 . A first symbol is associated with the original file and each additional symbol is associated with a respective update. For instance, if the upper leftmost symbol is clicked, the latest contents of the file are displayed, and in contrast, if the lower rightmost symbol is clicked, the oldest contents of the file recorded first on the tape medium are displayed. In certain embodiments, newer file contents are associated with upper left symbols. 
     One or more symbols do not entirely overlay another at the same position, i.e., they are displayed overlapping each other, so as to enable a user to distinguish the symbol to be clicked from the other(s). This icon display enables a user (e.g. GUI user, etc.) to readily understand the number of updates of files and execute rollback to each file by clicking an icon symbol. In embodiments, a file recorded on a tape storage medium and then deleted is denoted using an overlapping icon symbol indicating the file was deleted, as illustrated in  FIG. 3 . 
       FIG. 4  shows a flow chart of the behavior of LTFS for displaying an icon. At block  100 , the LTFS receives a request that an icon associated with a file be displayed. At block  102 , it is determined whether information on the file exists for the latest index. At block  104 , if the determination at block  102  is affirmative, an icon (e.g. icon of  FIG. 1 , etc.) is displayed. At block  106 , if the determination at block  102  is negative, it is determined whether an index exists one generation before the previous index. At block  118 , if the determination at block  106  is negative, the icon display method is completed. 
     At block  108 , if the determination at block  106  is affirmative, it is determined whether data exists in the file for the index one generation prior to the previous index. If the determination at block  108  is negative, the icon display method returns to block  106 . At block  110 , if the determination of block  108  is affirmative, it is determined whether an icon related to the file is displayed. At block  112 , if the determination at block  110  is negative, an overlapped icon is displayed with an indication that data was deleted (e.g. icon of  FIG. 3 , etc.) and, in turn, the icon display method returns to block  106 . 
     At block  114 , if the determination at block  110  is affirmative, it is determined if the file has been updated. If the determination at block  114  is negative, the icon display method returns to block  106 . At block  116 , if the determination at block  114  is affirmative, an overlapped icon is displayed (e.g. icon of  FIG. 2 , etc.) with an indication the data was updated and, in turn, the icon display method returns to block  106 . 
     In the case of rolling back to and then updating older file information, although rolled-back update information may be ignored, it may also be represented by a rolled-back overlapping symbol as illustrated in  FIG. 5 . 
     In another embodiment, a file that is recorded on a tape medium and remains not updated is denoted by an icon as illustrated in  FIG. 1 . A file that is recorded on a tape medium and then updated is denoted by adding colors to an icon depending on the number of updates, as illustrated in  FIG. 6 . For example, as shown in  FIG. 6 , if the upper white part of the icon is clicked, the latest contents of the file are displayed, and if the bottom dark part of the icon is clicked, the oldest contents of the file recorded first on the tape medium are displayed. In embodiments, regarding the other colored portions, newer contents may be associated with upper parts. In embodiments, a color for indicating the file has yet to be updated may be a fixed color or the same color as that of the icon itself. As shown in  FIG. 7 , a file recorded on a tape medium and then deleted may be denoted using an added color (e.g., black) indicating the file has been deleted. 
       FIG. 8  shows a flow chart of the behavior of LTFS for displaying an icon. At block  200 , the LTFS receives a request that an icon associated with a file be displayed. At block  202 , it is determined whether information on the file exists for the latest index. At block  204 , if the determination at block  202  is affirmative, a icon (e.g. icon of  FIG. 1 , etc.) is displayed. At block  206 , if the determination at block  202  is negative, it is determined whether an index exists one generation before the previous index. At block  218 , if the determination at block  206  is negative, the icon display method is completed. 
     At block  208 , if the determination at block  106  is affirmative, it is determined whether data exists in the file for the index one generation prior to the previous index. If the determination at block  208  is negative, the icon display method returns to block  206 . At block  210 , if the determination of block  208  is affirmative, it is determined whether an icon related to the file is displayed. At block  212 , if the determination at block  210  is negative, an icon is displayed (e.g. icon of  FIG. 7 , etc.) with added color and an indication that data was deleted and, in turn, the icon display method returns to block  206 . 
     At block  214 , if the determination at block  210  is affirmative, it is determined if the file has been updated. If the determination at block  214  is negative, the icon display method returns to block  206 . At block  216 , if the determination at block  214  is affirmative, an icon with added color indicating the data was updated is displayed (e.g. icon of  FIG. 6 , etc.) and, in turn, the icon display method returns to block  206 . 
     In the case of rolling back to and then updating older file information again, although rolled-back update information may be ignored, it may also be represented by adding a plurality of colors (e.g., blue and green) to an icon as illustrated in  FIG. 9 . For instance, the icon ma be partitioned by color stacks associated with updates upon a color associated with the rolled-back file. 
     In another embodiment, a file that is recorded on a tape medium and remains not updated is denoted by an icon as illustrated in  FIG. 1 . A file that is recorded on a tape medium and then updated is denoted by extending an icon depending on the number of updates as illustrated in  FIG. 10 . For example, if a left part of the icon is clicked, the latest contents of the file are displayed, and if a right part of the icon is clicked, the oldest contents of the file recorded first on the tape medium are displayed. In embodiments, regarding such symbols, newer contents are associated with more left parts. 
     In another embodiment, as shown in  FIG. 11 , a file recorded on a tape medium and then deleted is denoted using a height-changed icon (e.g., half the height of a conventional icon) indicating the file being deleted. 
       FIG. 12  shows a flow chart of the behavior of LTFS for displaying an icon. At block  300 , the LTFS receives a request that an icon associated with a file be displayed. At block  302 , it is determined whether information on the file exists for the latest index. At block  304 , if the determination at block  302  is affirmative, a icon (e.g. icon of  FIG. 1 , etc.) is displayed. At block  306 , if the determination at block  302  is negative, it is determined whether an index exists one generation before the previous index. At block  318 , if the determination at block  306  is negative, the icon display method is completed. 
     At block  308 , if the determination at block  306  is affirmative, it is determined whether data exists in the file for the index one generation prior to the previous index. If the determination at block  308  is negative, the icon display method returns to block  306 . At block  310 , if the determination of block  308  is affirmative, it is determined whether an icon related to the file is displayed. At block  312 , if the determination at block  310  is negative, an icon is displayed (e.g. icon of  FIG. 11 , etc.) with an indication that data was deleted and, in turn, the icon display method returns to block  306 . 
     At block  314 , if the determination at block  310  is affirmative, it is determined if the file has been updated. If the determination at block  314  is negative, the icon display method returns to block  306 . At block  316 , if the determination at block  314  is affirmative, an icon having deformation indicating the data was updated is displayed (e.g. icon of  FIG. 10 , etc.) and, in turn, the icon display method returns to block  306 . 
     In the case of rolling back to and then updating older file information again, although rolled-back update information may be ignored, it may also be represented by the combination of differently extended icons as illustrated in  FIG. 13 . 
     Generally, though the updated files are associated with width and deleted files are associated with height, as long as one deformation indicates data being deleted and another deformation indicates data being updated is sufficient. For example, the expansion and contraction associated with the updating or deleting may be in general differing directions. 
     Embodiments have been described herein referencing the rollback function of the linear tape file system (LTFS) in a tape medium, which is a type of storage, as an example. The idea, however, may also be broadly applied to any other storage mediums. In addition, the technical idea of the present invention may be implemented in various categories such as a method, a computer program product that which program instructions are stored which cause a computer to perform steps of a method, a system that implements a method, etc. 
     The embodiments of the present invention can be used advantageously, not only during formatting using the LTFS format, but also when an erase command is executed at the beginning of a tape medium. The embodiments of the present invention can be implemented not only as a method, but also as a program implementing the method, a system executing the method, and a tape medium using the method to record data.
An icon corresponds to a history of files related to a plurality of indexes. Each of the indexes and each of the files are additionally and synchronously recorded in storage as additional data. The icon displayed represents the status of data in the files in the storage. The displayed icon is manipulated to indicate whether no data exists in an associated file or to indicate that existing data in an associated file was updated.