Abstract:
A removable optical disk of the write once type is managed to minimize size of the control area for user data recorded on the disk. Instead of recording each recorded file indicating token (serial number) as each file is recorded, a maximum value file token having a numerical value greater than a previous maximum value token is recorded in the control area such that any optical recorder receiving the disk may start recording data using such maximum value token. If the file indicating token values reach the maximum value token, then a new maximum value token is created. A pseudo end of volume (EOV) value is maintained which points to a one of the addressable data storing ares of the disk which is allocated and not recorded as EOV. All allocated data storing areas with addresses greater than EOV are recorded in contiguously addressed data storing areas. When any data storing area having an address higher than EOV is left unrecorded, then EOV is updated to point to that unrecorded allocated data storing area. When either the maximum value token or EOV are changed or updated, both the EOV and maximum value token are recorded in the control area. Operations in a closed environment, super or umbrella allocation sizes and reduced EOV values are also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to using storage media, particularly write-once (preferably optical) media, for facilitating accessing recorded and unrecorded addressable areas and a new format for such storage media. 
     BACKGROUND OF THE INVENTION 
     Optical media of the write-once read-many (WORM) have been used for several years for permanently recording diverse data. Each WORM medium, usually a disk, also stores control information including a directory to the stored user or other data. It has been a usual practice to record successively in contiguous sectors or addressable areas of the disk or medium. That is, recording proceeds from a radial inward extremity, for example, toward a radial outward extremity. As the recording proceeds, all addressable areas between the radial inward extremity to the last recorded data/control are storing data. One approach to such recording is to record the non-directory data beginning at one radial extremity and record the directory beginning at a second radial extremity. In other systems, recording of directory and non-directory data proceeds from one extremity toward a second extremity. 
     It is desired to record data on a WORM medium wherein null or unrecorded addressable areas are interspersed with addressable areas storing data. It is also desired to operate with a WORM medium in a manner to minimize or reduce the number of addressable areas used by control information; i.e. a control of the medium, and the resulting medium, are desired to facilitate finding the last recorded data (end of the volume or EOV) as well as reducing the number of times control information is recorded, such as recording an EOV pointer and file-indicating tokens. Such tokens are alphanumeric or numeric values identifying files recorded on a medium. Such tokens are usually transparent to a computer user, i.e. the tokens are an internal mechanism of a data storing system. It is desired to reduce the number of addressable areas required for storing successively increasing values of an EOV pointer and file-indicating tokens. 
     DISCUSSION OF THE PRIOR ART 
     The U.S. Pat. No. 4,827,462 by Flannagan et al shows recording data on a WORM optical medium. This patent teaches that directory data are recorded beginning a first radial extremity of an optical disk and proceeding toward a second radial extremity of the optical disk while non-directory data are recorded beginning at the second radial extremity and proceeding toward the first radial extremity. All recording operations record data in a next vacant addressable area (disk sectors) such that no unrecorded but recordable addressable areas are interspersed between recorded addressable areas. When the recorded non-directory data meet the recorded directory data on a disk, that disk is full. 
     Diotte in U.S. Pat. No. 4,791,623 shows a specific intermingling of directory and non-directory data on a WORM disk in which the directory data are dispersed on the disk between non-directory data which have an addressing affinity for the nearest directory data. It appears that all addressable areas (sectors) are recorded into in a continuous sequential procedure. 
     It is desired to provide enhancements over the prior art which facilitate space-management and data accessing in a data-storing medium. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to minimize the number of addressable areas, such as disk sectors, assigned to storing control information by managing the manner in which file identifiers are generated and assigned to data being recorded. 
     It is a second object of the invention to facilitate finding an EOV when unrecorded, but recordable, areas remain dispersed amongst recorded areas. 
     In accordance with one aspect of the present invention, file-identifying tokens are assigned values less than a maximum token or &#34;max token&#34; value. Upon reaching the maximum token value, a new maximum token value is assigned. Upon starting recording operations, the last-recorded maximum token value is found; subsequent recording operations serially assign numbers to files being recorded that are greater than the maximum token value. Each new maximum token value has a value greater than the last-recorded maximum token value. 
     In accordance with a second aspect of the invention, an end of volume (EOV) pointer (address of a predetermined one of the addressable areas) has a current address related to a last allocated addressable area at the time EOV pointer was generated. Such last allocation may or may not contain data when the EOV pointer is generated. Data is recordable in addressable data-storing sectors having addresses greater than the EOV pointer address, hence the EOV pointer does not always point to a true end of the volume. Sectors recorded in addressable data-storing areas having addresses greater than the EOV pointer address preferably are recorded in contiguously addressed ones of the addressable data-storing areas. To find the true end of volume, a scan of addressable data-storing areas begins at a predetermined addressable data-storing area closely related to the EOV pointed to addressable data-storing area and proceeding to higher addressed addressable data-storing areas until an unrecorded one of the addressable areas is found. Such a finding terminates the scan and indicates where data recording may ensue. 
     In a third aspect of the invention the first two aspects are combined to efficiently manage operations related to a WORM medium. 
     The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWING 
     FIG. 1 is a simplified block diagram of a data-storing system in which the present invention is advantageously employed. 
     FIG. 2 is a diagrammatic plan view of an WORM optical disk usable in the FIG. 1 illustrated system. 
     FIG. 3 is a schematic diagram of continuation chains as may be recorded on the FIG. 2 illustrated disk. 
     FIGS. 4 through 7 are machine operations charts illustrating a practice of the present invention in the FIG. 1 illustrated system. 
     FIGS. 8 and 9 are simplified presentations of practicing the invention in a controlled environment, such as in an optical disk library system. 
    
    
     DETAILED DESCRIPTION 
     Referring now more particularly to the appended drawing, like numerals indicate like parts and structural features in the various FIGURES. In FIG. 1, host processor(s) 10 have a file manager program 11 which effects the machine operations shown in FIGS. 4-6 which implements the present invention. Peripheral controller 13 connects host processor or computer 10 to one or more WORM optical disk player-recorders in a usual manner. It should be noted that peripheral controller 13 may be a pluggable circuit board in a host computer, be embedded as a part of a host computer, an attachment card to a host computer, or be a separate standing unit connected to a host computer. Such peripheral controller may also be programmed in large part in a host processor. Main memory or random access memory (RAM) 12 is shared by file manager 11 and other programs executing in host processor 10. WORM optical player/recorder (also commonly referred to as a device) 14 is attached to peripheral controller 13 in a usual manner. 
     FIG. 2 illustrates in simplified form a plan view of a WORM optical disk removably insertable into player 14. Disk 15 includes a multiplicity of substantially concentric tracks, three of which are indicated by numerals 16, 17 and 18, respectively. A single spiral track is often used, no limitation thereto is intended. As used herein, the term concentric track also refers to each cirumvolution of a spiral track. Assuming a transducer (not shown) is parked during disk non-use at one radial extremity of the disk, track 18 may contain the volume medium information (VMI) information. As the VMI information increases with disk usage, tracks 17 and 16 may also be used for storing some of the VMI information. Other tracks, not shown store directory and other control information as well as user data, all as is known. 
     WORM optical disks often use so-called continuation chains for linking stored data of a file recorded on disk 15, whether the file is a control file as VMI or a user file. In creating a VMI continuation chain, FIG. 3, groups of disk sectors, herein termed addressable data-storing areas, form a constant sized allocation unit. Such groups may be compared with cluster allocations in DOS based systems. It is preferred for allocating groups of areas for the VMI continuation chain that such area groups be an integral multiple or submultiple of the number of areas in each track. In the illustrated embodiment, a group consists of a number of areas equal to the number of areas in one track; a spiral track is assumed. Once the beginning address, address of the first area or the area in a group having a lowest address, then the address of the last area in a group is easily calculated by adding the number of areas in a group to the lowest or first address. The terms greater, higher, and the like are intended to also include subtractive serial addressing, that is a first address may be the highest address in a disk 15 with subsequently allocated or used areas being addressable or identified by decreasing address numbers. 
     The FIG. 3 illustrated VMI continuation chain includes three groups 20, 21 and 22 of addressable data-storing areas 23. The three groups and their addressable data-storing areas 23 are linked by address pointers, as later described. First group 20 of areas 23 resides in track 18. A last area 24 of group 20 has a disk 15 address equal to the first area address plus (minus) the number of areas in the group. Second group 21 of areas 23 is found in track 17. Groups 20 and 21 are linked as follows. Area 25 of second group 21 has a reverse pointer to last area 24 of group 20 while area 24 has a forward pointer to area 25. Similarly, second group 21 is linked to third group 22 by address pointers in last area 26 of second group 21 and in first area 27 of third group 22. For purposes of discussion, area 28 in third group 22 is the last area in the continuation chain storing VMI data. Area 29 is a first null or vacant one of the addressable data-storing areas 23 in the VMI continuation chain. The operations involving this continuation chain will become apparent from FIGS. 4-6. 
     Allocated group 22 of the VMI continuation chain contains several null or vacant areas 29 and 29A. Data recording proceeds on disk 15 beginning in a addressable data-storing area 29B abutting group 22 areas of disk 15. This arrangement indicates null or vacant areas 29 and 29A between recorded ones of the areas 28 and 29B. Many instances of such intervening null areas 29B between spaced-apart recorded areas occur when using the procedures described for VMI continuation chain. Such intervening null areas also occur when user data file allocations exceed the number of such allocated areas used in a first recording operation following the allocation. In finding the true EOV, such as by scanning for a first null area (lowest address null area), such intervening null areas must be ignored. The present invention uses the EOV pointer value to logically &#34;jump&#34; over all of such intervening null areas for quickly finding the true end of volume. 
     Each of the addressable data-storing areas 23 have the same format. A first field 30 stores the later-described maximum value file-indicating token (max token). Second field 31 stores the end of volume (EOV) pointer. It is noted that for practicing the present invention, the EOV pointer does not always point to a true end of volume. Other control data not pertinent to an understanding of the present invention are found in third field 32. A reverse pointer 33 contains the address of the immediately preceding area 23, i.e. reverse pointer of area 25 points to area 24. A forward pointer 34 points to the next area 23 whether or not it contains data. That is, the forward pointer in area 28 of group 22 points to the next area 29 which is null, contains no recorded data. Area 28 is defined as the last area of the VMI continuation chain even though several null areas remain in the group allocation. Once third group 22 has its last area (unnumbered) filled with data, a fourth group (not shown) is allocated to the VMI chain and a forward pointer points to the first area (not shown) of such fourth group. At this time the EOV will point to the last area (not shown) of such fourth group, i.e. there are null areas between the last area containing data and the area pointed to by EOV pointer. Therefore, the EOV pointer points to the last area on the disk not available for new recording operations, whether null or full of data. Numeral 38 denotes that all data on disk 15 is recorded using continuation chains. While the VMI continuation chain is allocated in equal-sized allocation groups, other continuation chains may have variably sized groups of allocations. 
     FIG. 4 shows machine operations performed when a disk 15 is mounted or loaded into player 14. Disk 15 will have a VMI continuation chain and other data stored thereon. Machine step 40 represents mounting (inserting) a disk 15 into player 14. Player 14 includes the usual apparatus for detecting disk 15 mounting. Player 14 reports the disk 15 mount to file manager 11. File manager 11 responds by a command to player 14 effecting machine step 41 which finds the last sector (addressable data-storing area) of the VMI continuation chain (FIG. 3). Such last area 28 stores the current values of EOV and the max token. Area 28 is identified by its forward pointer 34 pointing to a next-adjacent null or vacant area 29. Machine step 42 reads field 30 to find the current max token value. The current max token value is stored by machine step 43 RAM 12 in a usual manner. Machine step 44 reads the current EOV from field 31 of area 28. At machine step 45 the current EOV value is stored in RAM 12. Numeral 46 indicates other machine operations are then performed. For example, the true end of volume is first found by accessing an area on disk 15 indicated by the current EOV value. In this regard, it is noted that the EOV value may point to the last allocated area or to the area immediately following (immediately following means an area having the next address value, the address of the last allocated area plus one). According to the invention, the true EOV is the first null sector following the EOV pointed to area. In some instances, there may be many contiguous data-filled areas having addresses greater than the EOV pointer. Other machine operations also occur at 46 such as recording data onto disk 15, reading data from disk 15, reporting status and the like, as is commonly practiced in the optical recording arts. 
     FIG. 5 illustrates, in simplified form, machine operations for storing a file of user data in contiguous addressable data-storing areas and for updating a file-indicating token value to identify this file. File manager 11 at machine step 50 receives a request for recording data as a file on disk 15. The current token value is increased by unity at machine step 51. Then, file manager 11 in machine step 52 compares the updated token value with the current value of the maximum value token (max token) retrieved from field 30 during the FIG. 4 described volume mounting. If the updated token value is less than the max token value, file manager 11 proceeds to machine step 53 recording the file on disk 15. Note that FIG. 5 omits the usual allocation step for acquiring data recording space on disk 15 for the file. After the received file is recorded, file manger 11 and other programming in host processor 10 (not shown) proceed to other machine operations. 
     If at machine step 52, the updated token value is not less than the max token value, then file manager 11 generates a new max token value to replace the old max token value. There is only one max token value effective at any one time. At machine step 55 file manager 11 makes a new max token by adding a predetermined value to the current max token, such as 64, 128, 256, etc. This predetermined value provides a numerical cushion enabling file manager 11 to conserve addressable areas of disk 15. In so doing, the max token indicates a minimal unique file-indicating token value usable to reinsitute recording on disk 15 as described with respect to FIG. 4. Such new max token value is selected to reduce the number of addressable areas 23 used for the VMI continuation chain by enabling recording the predetermined number of files on disk 15 without recording any additional file-indicating token values in the VMI continuation chain. Recording the new max token value in field 30 (in such a recording operation, all fields 30-34 are also recorded) in a next addressable data-storing area in the VMI continuation chain (FIG. 3), such as in null area 29, enables any player 14 to receive disk 15 and quickly begin assigning new unique file-indicating token values based upon the last-recorded max token value to files being received. Accordingly, in machine step 56, file manager 11 records the new max token value on disk 15 while retaining the value for executing machine step 52 each time a file is to be recorded on disk 15. After completing machine step 56, file manager 11 returns to machine steps 52 and 53. 
     FIG. 6 shows machine operations for updating and recording the max token value and the EOV value after each allocation of space for data recording. Certain systems status changes, such as upon a demount command, upon receiving an end of session indication and at other times, such as when a time out time expires, time of day, activity level indication change, etc., certain recording operations may be desired. Such desired recording occurs when updated values in EOV and max token have not been recorded when the status change is about to occur. In any constructed system, any one, some or all of the described criteria and methods, and their equivalents, may be used for practicing the present invention. 
     Upon receiving an allocation request over machine operations flow path entry at numeral 60 from other programs (not shown) in host processor 10, file manager 11 executes allocation step 61. Allocation step 61 allocates a number of the addressable data-storing areas, such as areas 23, for an ensuing recording operation(s). Two known modes of allocation may be used, both modes having variants, as is known. As usual, in each allocation contiguous null areas are allocated. In a first mode, allocation step 61 allocates a number of areas sufficient to store data of a file or file portion to be recorded. The other programs (not shown) of host processor 10 indicate to file manager 11 the desired number of areas. In the next ensuing recording operation, data are recorded in all of the just-allocated areas. In a second mode, file manager 61 in allocation step 61 allocates a number of areas exceeding the number of areas required in the next ensuing recording operation for the just-allocated areas. Host processor 10 may indicate the number of desired areas to be allocated or the allocation request may inferentially indicate that a predetermined number of areas are to be allocated. That is, the allocation request may include information to be interpreted by file manager 11 as indicating a given number of areas for the allocation. In the present illustration, the mode used is a criterion for updating and recording the EOV value. Whenever the selection of the number of areas to be allocated may be completely controlled by host processor 10 independently of file manager 11, then host processor 10 other programs (not shown) may send an EOV update indicating flag to file manager 11 commanding updating the EOV value either after the allocation step 61 or at some other time. 
     The invention also makes the allocation steps independent of the recording steps. That is, usually recording closely follows allocation of areas; the invention enables leaving allocated unused areas for much later recording yet providing rapid identification of the true end of volume for future allocations. 
     Upon completing the allocation, file manager proceeds to machine step 62 for determining the selected control mode for updating EOV. The &#34;instant&#34; EOV update mode results in updating the EOV value immediately after the allocation step 61 effected an allocation in its second mode; otherwise, any allocation completed in the first mode results in not updating the EOV value. Assuming the instant mode, file manager 11 in machine step 63 determines the mode used in the prior allocation, i.e. if in the second mode null areas will occur. In this instance, file manager 11 proceeds to machine step 64 to generate an updated EOV value. The updated EOV value is stored in RAM 12 for recording on disk 15 by file manager 11 until the later described machine operations relating to the max token have been completed. 
     If at machine step 63, the last allocation step 61 execution was in the first mode, then file manager 11 proceeds to machine step 65 for evaluating the new file-indicating token value with respect to the current max token value. Machine step 65 is also executed from machine steps 64 or 66. Machine step 64 is identical to previously described machine step 52 of FIG. 5. 
     If the EOV mode at machine step 62 is &#34;other&#34;, then file manager 11 in machine step 66 ascertains whether or not criteria other than leaving null areas in an allocated group of sectors require an immediate or deferred generation of a new EOV value. Register 66C stores control data from other programs (not shown) of host processor 10 which may indicate a new EOV value is required. Diverse criteria may be used either singly or in predetermined combinations, all depending on system design and programming. The examples given are not exhaustive of criteria useable for effecting updating the EOV value. Examples given as being in register 66C are expiration of a time-out timer (TOT), reaching a predetermined time of day (TOD), user data file allocation may or may not result in leaving null areas after the first ensuing recording (UN) or the type of and intensity of activity (ACT) is such in a recent computing past indicates an advantage of updating the EOV value. Such activity may include a predetermined number of successive allocations in repeated executions of allocation step 61 or a predetermined number of areas have been allocated by such executions of machine step 61. From the above description, it is readily seen that a great variety of criteria may be used for activating an update to the EOV value. 
     In accordance with one aspect of the ACT control of register 66C, allocation step 61 performs an umbrella or super allocation of space in anticipation of upcoming allocations to be performed within the umbrella allocated space. The EOV pointer is advanced to point to the end of the umbrella allocated space. Whenever the umbrella allocated space is exceeded, then a new umbrella space is allocated and the EOV pointer advanced for pointing to the end of that space. That is, the EOV pointer can be advanced to the highest address being currently considered for use and be written to the VMI continuation chain. The umbrella EOV pointer may be the max token 30; thereby at each umbrella allocation the VMI chain is updated as described herein. 
     As long as the disk medium is contained within player 14 and the receiver 14R is under machine control, the disk medium can be considered as being in a closed environment, such as later described with respect to FIGS. 8 and 9. The procedures set forth in FIG. 9 can be applied to each individual player; in such an instance, a shadow EOV is stored in a retentive store, such as store 92 of FIG. 8. This procedure further limits the number of times the max token value and the EOV value have to be recorded in the VMI continuation chain. 
     In the latter described procedure, at dismount command or at some predetermined other time (elapsed time, number of allocations, etc) file manager 11 analyzes the allocations made in the umbrella allocation area. The analyzed allocation status may indicate that the umbrella EOV could be made smaller in value. At this point in time, both the umbrella EOV and max token values (whether different or the same values) can be reduced whenever the allocation of space actually being used is proceeding such that all allocated sectors or areas are being filled (there are not allocated and unrecorded areas or sectors in recent allocations) such that the least permitted EOV value is less than the current EOV value. From the above few paragraphs, it is readily seen that there are many variations of control possible when practicing the present invention. 
     Machine step 65 is entered from either machine step 66 indicating no new EOV value is to be generated, from machine step 64 or from machine step 63. In executing machine step 65, if a new max token value is required, file manager 11 executes machine step 67 for generating a new max token value; machine step 67 is identical to previously described machine step 55 of FIG. 5. From either machine step 65 or 67, file manager 11 in machine step 68 reads RAM 12 to determined whether or not either the EOV value or the max token value were updated in the current pass through the illustrated machine operations. If either one of the EOV or max token values were updated, then at machine step 69 a new entry in the VMI continuation chain (FIG. 3) is created and recorded in its first null sector. In FIG. 3, area 28 is the current last area of the VMI continuation chain resulting in the new VMI entry being recorded in area 29, the null area next to area 28. All unchanged information of the current VMI entry is also recorded. 
     From either machine step 68 (no updating of EOV or max token) or from machine step 69, data recording ensues in machine step 70 whenever data are to be recorded. Such recording operation may have been queued in host processor 10 or may require other activity beyond the present description. From machine step 70, file manager 11 and other programming of host processor 10 proceed to other machine operations. 
     Based upon systems considerations, certain system status changes may require recording an unrecorded EOV value or max token value. If a volume or disk demount command is given, then from machine step 75 file manager 11 proceeds over machine operations path 80 to machine step 81. In machine step 81, file manager 11 determines by examining RAM 12 contents whether or not a new VMI entry is required. In addition to having a current EOV value or max token value in file manager 11 that is different from the currently stored values in the VMI continuation chain, other control data changes may indicate a need for building and recording a new VMI entry. In this instance, machine steps 68 et seq may be executed for including any unrecorded updated values of EOV or max token. If no recording need is required, the other operations ensue via operations path 71 are performed. Other systems status that requires attention include an end of a disk session (without demount, for example) detected at machine step 76 or another system status (not described) detected at machine step 77. 
     FIG. 7 illustrates an initialization of disk 15. A so-called scratch disk 15 is mounted for operation in player 14 at machine step 80 and initialized for recording in a usual manner. Mounting may be manual or automatic. At machine step 81, file manager 11 responds to completion of the machine step 80 initialization to generate an initial max token value which may be 512, for example. File-indicating token values may start with unity, or any other integral value, preferably positive. Machine step 82 generates initial control chains needed for recording on disk 15, such chains will include allocating group 20 of the VMI continuation chain in FIG. 3. File manager 11 at machine step 83 then generates the first EOV value pointing to the last allocated addressable data-storing area in these control chains. File manager 11 then records the initial max token value and EOV value in the first allocated area of group 20. 
     FIGS. 8 and 9 illustrate, in simplified form, an embodiment employing the present invention in a closed operating environment, i.e. an environment in which the disk media is continuously under automatic machine control whether mounted on a disk player for recording or playback operations or stored elsewhere, such as in a library array of storage slots. One or more using units 90, such as host processor 10 of FIG. 1, are connected to a library controller 91. Library controller 91 may replace controller 13 and file manager 11 of FIG. 1, or parts thereof as befits a given system design. The illustrated closed environment is effected by a library system including the library controller 91 which has a magnetic disk storage unit 92 (or other form of retentive storage) for storing control information. Disk storage array 93 which can be a rectilinear array, tubular array, etc, stores a plurality of disk media in a number of addressable disk storage compartments or slots. Automatic disk accessor 94 addressably accesses individual disk storage compartments or slots of array 91 for storing disk media in respective ones of the compartments and for fetching disk media stored in ones of the compartments. Disk accessor 94 may have one or more travelling elevators with suitable disk media handling apparatus, as is known. Disk accessor 94 transports the disk media, upon library controller 91 commands, to and from addressed ones of a plurality of disk players 95, each of which has a disk receiver such as receiver 14R, such transport being represented by the triad lines 96. Disk players 95 are controlled by library controller 91 as indicated by line 97. Data transfers also travel over a cable included in line 97, as is known in the art. The above-described apparatus keeps all disk media under automatic machine control of library controller 91 as commanded and referenced by using units 90. Disk media are controllably inputted into and removed from disk array 93 via IO or input-output station 98. The machine control of IO 98 will become apparent from FIG. 9. It is to be understood that disk accessor 94 accesses IO 98 as if it were one or more ones of the addressable compartments of array 91. IO 98 may have one input port for inputting disk media serially into array 91 and one output port for removing disk media from array 91; any number of ports may be provided for effecting this input and removal function. IO 98 may be either manually or automatically loaded or unloaded. 
     In FIG. 9, the FIG. 8 illustrated library system at machine step 100 receives an optical disk in IO 98 for storage in array 91 and usage in the library system under continuous control of library controller 91. IO 98 has a suitable sensing mechanism (not shown) for detecting and indicating a received disk medium. Library controller 91 responds to such indication for actuating disk actuator 94 to transport the received disk medium to an addressed one of the optical disk players 95. At this point in time, library controller 91 actuates the addressed disk player 95 holding the input disk medium to find its EOV. For a scratch or unrecorded disk medium, library controller 91 commands a format of the scratch disk and generation of an initial EOV which is not recorded on the input disk medium, rather the initial EOV is recorded as a shadow EOV in retentive store 92 along with an internal designation for the input disk medium. Such initial EOV is stored as a so-called shadow EOV. For a partially or fully recorded input disk, the EOV is automatically determined as described for FIG. 4. That determined EOV is then recorded in retentive store 92 as the shadow EOV. Note that at this point in time, the max token value is not necessarily processed; it being understood that the max token value, if any, of a received disk medium may be read and stored alongside the shadow EOV. As mentioned above, accessing the stored EOV and other information about the received disk medium, is by an internal designation of the disk medium. Such internal designation may take any one of a plurality of forms. By way of example, the internal designation may be the array 93 compartment address in which the received disk medium is to be stored while in the closed environment, may be a serial number of the received disk medium for facilitating using any one of the addressable array 93 compartments to store the disk medium, and the like. 
     Machine step 102 of FIG. 9 indicates that a plurality of operations may be performed on the received disk medium while it is resident in the library system or closed environment. Each time a new EOV is generated for any of the disk media in the library system, the shadow EOV is updated with the latest value of the shadow EOV being retentively stored in store 92. During this period of residency of the disk media, the max token values of the all of the library system controlled disk media are altered in any of the VMI chains of such disk media. 
     At some time, it is desired to export or remove some of the library system controlled disk media. Library controller 91 receives from a one of the using units 90 a command to remove a given disk medium, or library controller 91 may have evaluation programming which matches the current shadow EOV value with a threshold value for ascertaining whether or not significant or usable recording space still is on which disk media. A least recently used (LRU) control may be used to select a disk medium for export from the library system. In any event, at machine step 104, library controller 91 prepares to export a disk medium. At machine step 105 a max token value is generated as being a value &#34;n&#34;, n is an integer, greater than the current shadow token value. If the volume capacity of the disk medium to be exported has been filled, then the max token value is set to the medium capacity and the EOV is set to the max token value for indicating that the disk medium is full. Then library controller 91 records the max token value, along with other control information as shown in FIG. 3, in the VMI continuation chain of the disk medium to be exported. Upon successfully completing updating the VMI chain, the disk medium is physically exported or removed from the library system at machine step 107 via IO 98. Library controller 91 then updates retentive store 92 to reflect such exportation. Such control data may also be reported to interested ones of the using units 90 in a usual manner. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.