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Guide to OpenVMS File Applications

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An interactive session is controlled by these Edit/FDL utility scripts. You can invoke a script in two ways:

  • You can select the INVOKE command from the main menu and then choose your script. When you answer the script questions, the Edit/FDL utility displays a list of FDL attributes and their assigned values. At this point, you can use the Edit/FDL utility commands to further modify the attribute values or to end the editing session.
  • You can begin a script by entering a DCL command in the following form:


    This command bypasses the main menu to directly display the menu for the selected script.

Example 4-1 shows a sample session with the Edit/FDL utility.

Example 4-1 Sample Edit/FDL Utility Session

                  OpenVMS FDL Editor

  Add     to insert one or more lines into the FDL definition
  Delete  to delete one or more lines from the FDL definition
  Exit    to leave the FDL Editor after creating the FDL file
  Help    to obtain information about the FDL Editor
(1)  Invoke  to initiate a script of related questions
  Modify  to change existing line(s) in the FDL definition
  Quit    to abort the FDL Editor with no FDL file creation
  Set     to specify FDL Editor characteristics
  View    to display the current FDL Definition
(2)  Main Editor Function            (Keyword)[Help] : INVOKE

                Script Title Selection

  Add_Key       modeling and addition of a new index's parameters
  Delete_Key    removal of the highest index's parameters
  Indexed       modeling of parameters for an entire Indexed file
(3)  Optimize      tuning of all indexes' parameters using file statistics
  Relative      selection of parameters for a Relative file
  Sequential    selection of parameters for a Sequential file
  Touchup       remodeling of parameters for a particular index
(4)  Editing Script Title            (Keyword)[-] : INDEXED
(5)  Target disk volume Cluster Size (1-1Giga)[3]    : 3
(6)  Number of Keys to Define        (1-255)[1]      : 1

  Line    Bucket Size vs Index Depth      as a 2 dimensional plot
  Fill    Bucket Size vs     Load Fill Percent     vs Index Depth
(7)  Key     Bucket Size vs         Key Length        vs Index Depth
  Record  Bucket Size vs        Record Size        vs Index Depth
  Init    Bucket Size vs Initial Load Record Count vs Index Depth
  Add     Bucket Size vs  Additional Record Count  vs Index Depth
(8)  Graph type to display           (Keyword)[Line] : LINE
(9)  Number of Records that will be Initially Loaded
  into the File                   (0-1Giga)[-]  : 100000
(10)  (Fast_Convert NoFast_Convert RMS_Puts)
  Initial File Load Method        (Keyword)[Fast] : FAST
(11)  Number of Additional Records to be Added After
  the Initial File Load           (0-1Giga)[0]    : 0

(12)  Key  0 Load Fill Percent        (50-100)[100]   : 100
(13)  (Fixed Variable)
  Record Format                   (Keyword)[Var]  : VARIABLE
(14)  Mean Record Size                (1-32229)[-]    : 80
(15)  Maximum Record Size             (0,80-32229)[0] : 0

(16)  (Bin2 Bin4  Bin8  Int2  Int4  Int8  Decimal  String  Collated
      Dbin2 Dbin4 Dbin8 Dint2 Dint4 Dint8 Ddecimal Dstring Dcollated)
  Key  0 Data Type                (Keyword)[Str]  : STRING
(17)  Key  0 Segmentation desired     (Yes/No)[No]    : NO
(18)  Key  0 Length                   (1-255)[-]      : 9
(19)  Key  0 Position                 (0-32220)[0]    : 0
(20)  Key  0 Duplicates allowed       (Yes/No)[No]    : NO
(21)  File Prolog Version             (0-3)[3]        : 3
(22)  Data Key Compression desired    (Yes/No)[Yes]   : YES
(23)  Data Record Compression desired (Yes/No)[Yes]   : YES
(24)  Index Compression desired       (Yes/No)[Yes]   : YES

  Index 7|
  Depth 5|
        3|  3 3
        2|      2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
        1|                                                  1 1 1 1 1 1 1 1
         +- + - - - + - - - - + - - - - + - - - - + - - - - + - - - - + - +
(25)            1       5        10        15        20        25        30  32
                          Bucket Size (number of blocks)

   PV-Prolog Version       3 KT-Key  0 Type     String EM-Emphasis  Flatter ( 3)
   DK-Dup Key  0 Values   No KL-Key  0 Length        9 KP-Key  0 Position      0
   RC-Data Record Comp    0% KC-Data Key Comp       0% IC-Index Record Comp   0%
   BF-Bucket Fill       100% RF-Record Format Variable RS-Mean Record Size    80
   LM-Load Method  Fast_Conv IL-Initial Load    100000 AR-Added Records        0
          (Type "FD" to Finish Design)
(26)          Which File Parameter (Mnemonic)[refresh]     : FD
(27)  Text for FDL Title Section      (1-126 chars)[null]
(28)  Data File file-spec             (1-126 chars)[null]
(29)  (Carriage_Return Fortran None Print)
  Carriage Control                (Keyword)[Carr] : CARRIAGE_RETURN

  Emphasis Used In Defining Default:      (    Flatter_files   )
  Suggested Bucket Sizes:                 (      3     3    27 )
(30)  Number of Levels in Index:              (      2     2     1 )
  Number of Buckets in Index:             (     72    72     1 )
  Pages Required to Cache Index:          (    216   216    27 )
  Processing Used to Search Index:        (    168   168   766 )
(31)  Key  0 Bucket Size              (1-63)[3]       : 3
(32)  Key  0 Name                     (1-32 chars)[null]
(33)  Global Buffers desired          (Yes/No)[No]    : NO
(34)  The Depth of Key  0 is Estimated to be No Greater
  than 2 Index levels, which is 3 Total levels.
(35)  Press RETURN to continue (^Z for Main Menu)

                    OpenVMS FDL Editor

  Add     to insert one or more lines into the FDL definition
  Delete  to delete one or more lines from the FDL definition
  Exit    to leave the FDL Editor after creating the FDL file
(36)  Help    to obtain information about the FDL Editor
  Invoke  to initiate a script of related questions
  Modify  to change existing line(s) in the FDL definition
  Quit    to abort the FDL Editor with no FDL file creation
  Set     to specify FDL Editor characteristics
  View    to display the current FDL Definition
(37)  Main Editor Function            (Keyword)[Help] : EXIT
  1. The Main Editor Function menu displays the Edit/FDL utility commands.
  2. The INVOKE command displays the Script Title Selection menu. Note that HELP is the default command so if you want online help, just press the Return key.
  3. The Script Title Selection menu shows the seven scripts you can choose to help you design your file. There is no default so you must explicitly select one of the scripts.
  4. Choose the INDEXED script to design an indexed data file.
  5. Choose a disk cluster size of three.
  6. Define only one key---the primary key.
  7. This menu provides a selection of graphic display types.
  8. Select a line plot display.
  9. Select 100,000 records to be loaded initially.
  10. Select the CONVERT/FAST_LOAD method of loading records into the data file.
  11. Opt for no additional records after the initial load.
  12. Elect a fill level of 100 percent for the primary index buckets.
  13. Choose the variable-length record format.
  14. Select an average record size of 80 characters.
  15. Select an unlimited maximum record size.
  16. Select the string data type for the primary key.


    The string data-type keys include STRING, DSTRING, COLLATED and DCOLLATED keys.
  17. Opt to disallow segmentation in the primary key.
  18. Set the length of the primary key to 9 bytes.
  19. Define the initial position of the primary key at column 0.
  20. Opt to disallow duplicates of the primary key.
  21. Choose the Prolog 3 version.
  22. Select data key compression.
  23. Select data record compression.
  24. Select index compression.
  25. This is a line plot showing bucket size against index depth.
  26. Type "FD" to finish the design session.
  27. Enter the title of your FDL file specification.
  28. Enter the file specification of your data file.
  29. Select the CARRIAGE_RETURN carriage control.
  30. This display shows the tuning emphasis you chose to design your file. It also shows suggested bucket sizes for various index level depths and other tuning information.
  31. Select the default bucket size for the primary key.
  32. Enter the name of the primary key.
  33. Choose whether you want global buffers.
  34. This message shows the depth of the primary key index and gives the total number of levels.
  35. Press the Return key to display the main menu.
  36. This is the main menu.
  37. Use the EXIT command to exit the editor and to create the FDL file.
  38. This message shows the resulting FDL file specification and the number of lines it contains.

Note that the example uses most of the suggested defaults. There are three ways to accept defaults:

  • Press the Return key without entering a value.
  • Use the /RESPONSES=AUTOMATIC qualifier when you invoke the Edit/FDL utility.
  • Use the following sequence:
    1. Select the SET command from the main menu.
    2. Select RESPONSES from the SET menu.
    3. Accept the default (AUTO) when the Edit/FDL utility prompts for "Default responses in script."
Key compression and index compression are not acceptable options when you select a collated key data type.

When the Edit/FDL utility creates an FDL file, it groups the attributes into major sections. The section headings are called primary attributes, and the attributes within a primary section are called secondary attributes. Certain secondary attributes contain a third level of attributes called qualifiers.

The objective of using the Edit/FDL utility is to create an FDL file with optimum values for the various attributes. An FDL file contains a list of the primary and secondary attributes with related qualifiers. If a primary or secondary attribute does not appear in the FDL file, it is assigned its default value.

Example 4-2 shows an FDL file. IDENT, SYSTEM, FILE, RECORD, AREA n, and KEY n are primary attributes; the others are secondary attributes.

Example 4-2 Sample FDL File

" 1-MAR-1993 14:07:46   OpenVMS FDL Editor"

        SOURCE                  VMS
        NAME                    DISK$RMS:[RMSTEST]INDEXED.DAT;3
        ORGANIZATION            indexed
        OWNER                   [RMS1,TEST]
        PROTECTION              (system:RWED, owner:RWED, group:RE, world:)

        BLOCK_SPAN              yes
        CARRIAGE_CONTROL        none
        FORMAT                  variable
        SIZE                    2048

        ALLOCATION              233
        BEST_TRY_CONTIGUOUS     yes
        BUCKET_SIZE             5
        EXTENSION               60
        ALLOCATION              5
        BEST_TRY_CONTIGUOUS     yes
        BUCKET_SIZE             5
        EXTENSION               5

        ALLOCATION              18
        BEST_TRY_CONTIGUOUS     yes
        BUCKET_SIZE             3
        EXTENSION               6

        CHANGES                 no
        DATA_AREA               0
        DATA_FILL               100
        DUPLICATES              no
        INDEX_AREA              1
        INDEX_COMPRESSION       no
        INDEX_FILL              100
        LEVEL1_INDEX_AREA       1
        NAME                    "NUM"
        NULL_KEY                no
        PROLOG                  3
        SEG0_LENGTH             8
        SEG0_POSITION           0
        TYPE                    bin8

        CHANGES                 yes
        DATA_AREA               2
        DATA_FILL               100
        DUPLICATES              yes
        INDEX_AREA              2
        INDEX_COMPRESSION       yes
        INDEX_FILL              100
        LEVEL1_INDEX_AREA       2
        NAME                    "NAME"
        NULL_KEY                yes
        NULL_VALUE              0
        SEG0_LENGTH             39
        SEG0_POSITION           9
        TYPE                    string Designing an FDL File

When you want to create an FDL file, you invoke the Edit/FDL utility with a DCL command in the following form:

EDIT/FDL/CREATE fdl-filespec

The /CREATE qualifier specifies that you want to create an FDL file with the name entered in the fdl-filespec parameter. When the Edit/FDL utility displays the main menu, select the INVOKE command. In response to the INVOKE command, the Edit/FDL utility prompts you for a script. The only appropriate scripts for creating a file are INDEXED, RELATIVE, and SEQUENTIAL.

As discussed previously, you can enter a script directly by specifying the /SCRIPT qualifier on the DCL command line. For example, enter the following command to create an indexed FDL file:


When you select the script, the Edit/FDL utility prompts you for information about the data file. Each prompt consists of a short question, a range of acceptable values (for example, 50-100) or the value type (for example, Keyword, YES/NO, and so forth) in parentheses, and the default answer in brackets. One of the questions in the INDEXED script is shown as follows:

Number of Keys to Define (1-255)[1] :

In this example, the Edit/FDL utility prompts you for the number of keys you want to define for an indexed data file. The Edit/FDL utility accepts any number from 1 to 255. If you do not specify a value, it assumes that you want to define one key only, the primary key. To accept the default value, press the Return key.

If the Edit/FDL utility requires that you enter a value (that is, no default value is specified for the response), it includes a dash within brackets [-].

When you specify the SEQUENTIAL script or the RELATIVE script, the Edit/FDL utility returns you to the main menu level after finishing the dialog. When you specify the INDEXED script, one of the prompts requests your choice of a design graphics display: a Line_Plot graph or a Surface_Plot graph. After finishing the dialog, the Edit/FDL utility displays the selected graph to help you make your final design choice.

The Line_Plot graph plots bucket size against index depth. All things equal, the size of the buckets determines the number of levels in the index, and the number of levels has a direct effect on the run-time performance of an indexed file. Fewer levels generally reduce the average number of keys searched when the index tree is traversed. However, fewer levels imply more records per data bucket and may cause longer data bucket search times. Thus, the Line_Plot graph helps you decide on the best bucket size for your application. Figure 4-1 shows a Line_Plot graph.

Figure 4-1 Line_Plot Graph

As shown in Figure 4-1, a bucket size of 1 block results in an index with five levels. Increasing the bucket size to 2 blocks reduces the number of index levels to four, but an increase to 5 blocks does not reduce the number of index levels at all. A bucket size of 7 blocks, however, reduces the number of index levels to three.

When you choose the bucket size, remember that the graphs do not display the data level. For example, if you want three levels in the file, then you must limit the number of index levels to two.

The Surface_Plot graphics mode lets you choose a range of values to see their effects. The Edit/FDL utility prompts you to enter a lower and upper bound for one of the following values:

  • Load fill percent
  • Key length
  • Record size
  • Initial load record count
  • Additional record count

The selected range is displayed along the graph's vertical axis.

The variable on the graph's horizontal axis is bucket size. The numbers in the field portion of the graph show the number of levels at each bucket size for each of the other values.

Figure 4-2 is a Surface_Plot graph that shows a range of values for initial fill factors ranging from 100% to 40%.

Figure 4-2 Surface_Plot Graph

The area on the graph within the slash marks represents combinations that RMS finds acceptable. In Figure 4-2, a fill factor of 70% and a bucket size of 10 blocks is the optimum combination. A fill factor of 70% and a bucket size of 15 blocks is a relatively poor combination because it falls outside of the slash boundaries.

If you are sure the information you supplied to the Edit/FDL utility is valid, the best values are those that lie along the left-hand boundary next to the slash marks. If you are not sure that your information is valid, you should choose a value that lies more to the right of the slash boundary.

When you complete the dialog and the Edit/FDL utility presents the graph, you can make changes to certain attributes of the proposed data file. The design is not complete until you specify "FD" for "Finish Design," at which point the Edit/FDL utility asks a few more questions. You then have the opportunity to return to the main menu to view the file attributes that the Edit/FDL utility has created.

Figure 4-3 shows the attributes that you can alter when the Edit/FDL utility displays the graph. Note that each attribute has a 2-letter mnemonic. To alter an attribute, you specify the corresponding mnemonic. To refresh the display, press the Return key. To begin the final design phase, enter "FD."

Figure 4-3 Design Mnemonics

During the final design phase, the Edit/FDL utility gives you an opportunity to supply values for such attributes as TITLE, an optional primary that allows you to label the FDL file. (Most of these questions are also applicable to designing sequential and relative files.) When you have answered the questions, the Edit/FDL utility assigns the values to the FDL attributes and returns you to the main menu level to display the resulting FDL file.

At the main menu, you can select the ADD command to assign values to any attribute the script omitted. Remember that if an attribute does not appear in the FDL file, it assumes the default value. (For a list of the default values for each attribute, see the OpenVMS Record Management Utilities Reference Manual.) To modify an attribute, use the MODIFY command, and to delete an attribute, use the DELETE command.

To create the displayed FDL file, select the EXIT command. To abort the session without creating an FDL file, select the QUIT command.

4.1.3 Using the FDL Routines

You can also define file-creation characteristics with the FDL utility routines. The FDL routines provide you with the functions of the File Definition Language, and they allow you to set file creation characteristics from within your application.

There are four FDL routines:

FDL$CREATE Creates a file from an FDL specification, and then closes the file. See Section 4.2.4 for more information.
FDL$GENERATE Produces an FDL specification by interpreting a set of control blocks. It then writes the FDL specification either to an FDL file or to a character string.
FDL$PARSE Parses an FDL specification, allocates control blocks, and then fills in the relevant fields.
FDL$RELEASE Deallocates the virtual memory used by the control blocks created by FDL$PARSE. You must use FDL$PARSE to fill in (to populate) the control blocks if you plan to release the memory with FDL$RELEASE later.

Because the FDL$GENERATE, FDL$PARSE, and FDL$RELEASE routines allow you to use the run-time, as well as the creation-time, features of RMS, you must call them from a language that can access the control block fields that specify the CONNECT options. This may be difficult from a high-level language.

Example 4-3 shows how to call the FDL$PARSE and FDL$GENERATE routines from a Pascal program.

Example 4-3 Using FDL Routines in a Pascal Program

PROGRAM example2 (input,output,order_master);

(* This program fills in its own FAB, RAB, and  *)
(* XABs by calling FDL$PARSE and then generates *)
(* an FDL specification by calling FDL$GENERATE.*)
(* It requires an existing input FDL file       *)
(* (TESTING.FDL) for FDL$PARSE to parse.        *)

(*+                                             *)
(*-                                             *)
        $BIT1 = [BIT(1),UNSAFE] BOOLEAN;

        1: (FDL$_FDLDEF_BITS : [BYTE(1)] RECORD END;
        2: (FDL$V_SIGNAL : [POS(0)] $BIT1;
                (* Signal errors; don't return          *)
            FDL$V_FDL_STRING : [POS(1)] $BIT1;
                (* Main FDL spec is a char string       *)
            FDL$V_DEFAULT_STRING : [POS(2)] $BIT1;
                (* Default FDL spec is a char string    *)
            FDL$V_FULL_OUTPUT : [POS(3)] $BIT1;
                (* Produce a complete FDL spec          *)

    mail_order =  RECORD
                  order_num : [KEY(0)] INTEGER;
                  name : PACKED ARRAY[1..20] OF CHAR;
                  address : PACKED ARRAY[1..20] OF CHAR;
                  city : PACKED ARRAY[1..19] OF CHAR;
                  state : PACKED ARRAY[1..2] OF CHAR;
                  zip_code : [KEY(1)] PACKED ARRAY[1..5]
                       OF CHAR;
                  item_num : [KEY(2)] INTEGER;
                  shipping : REAL;
    order_file  = [UNSAFE] FILE OF mail_order;
    ptr_to_FAB  = ^FAB$TYPE;
    ptr_to_RAB  = ^RAB$TYPE;
    byte = 0..255;

    order_master : order_file;
    flags        : FDL2$TYPE;
    order_rec    : mail_order;
    temp_FAB     : ptr_to_FAB;
    temp_RAB     : ptr_to_RAB;
    status       : integer;

  (%REF cond_val: INTEGER;
   %IMMED num: INTEGER := %immed 0;

         OF CHAR;
         OF CHAR) : INTEGER;


 if not odd (status) then LIB$SIGNAL(status);
    flags::byte := 0;
    status := FDL$GENERATE (flags,
 if not odd (status) then LIB$SIGNAL(status);


For more information about FDL routines, see the OpenVMS Utility Routines Manual.

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