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Data Division in the Communication Module Communication Section In a COBOL program the Communication Descriptionentries (CD) represent the highest level of organization in the Communication Section. The COMMUNICATION SECTION header is followed by a CD entry consisting of a level indicator, a data-name and a series of independent clauses. These clauses indicate the queues and subqueues, the message date and time, the source, the text length, the status and end keys, and message count of input. They also specify the destination count, the text length, the status and error keys, and destinations for output. For ANS85 only: For an input-output CD entry the clauses specify the message date, message time, symbolic terminal, text length, and key and status key. The entry itself is terminated by a period. These record areas can be implicitly redefined by user-specified record description entries following the various CD clauses. The Communication Description - Complete Entry Skeleton Function. The CD specifies the interface area between the MCS and a COBOL program. General Formats. Format 1.Format 2.For ANS85 only: Format 3.Syntax Rules. All Formats. 1. A CD must appear only in the Communication Section. Formats 1 and (3 - ANS85). 2. Within a single program, the INITIAL clausecan be specified in only one CD. The INITIAL clause must not be used in a program that specifies the USING phrase of the PROCEDURE DIVISION Header. (See the section The PROCEDURE DIVISION Header in the chapter Program Definition in your Language Reference.) 3. Except for the INITIAL clause, the optional clauses can be written in any order. 4. If neither option in the format is specified, a level 01 data description entry must follow the CD entry. Either option can be followed by a level 01 data description entry. 5. Record description entries following an input CD implicitly redefine this record and must describe a record of exactly 87 standard data format characters. Multiple redefinitions of this record are permitted; however, only the first redefinition can contain VALUE clauses. However, the MCS will always reference the record according to the data descriptions defined in General Rule 4. 6. Data-name-1, data-name-2,..., data-name-11 must be unique within the CD. Within this series, any data-name can be replaced by the reserved word FILLER. Format 2. 7. For ANS85 only: The optional clauses can be written in any order. 8. If none of the optional clauses of the CD is specified, a level 01 data description entry must follow the CD entry. 9. Record descriptions following an output CD implicitly redefine this record. Multiple redefinitions of this record are permitted; however, only the first redefinition can contain VALUE clauses. The MCS will always reference the record according to the data descriptions defined in General Rule 18. 10. Data-name-1, data-name-2,..., data-name-5 must be unique in a CD. 11. If the DESTINATION TABLE OCCURS clauseis not specified, one ERROR KEY and one SYMBOLIC DESTINATION areais assumed. In this case, neither subscripting nor indexing is permitted when referencing these data items. 12. If the DESTINATION TABLE OCCURS clause is specified, data-name-4 and data-name-5 can only be referred to by subscripting or indexing. 13. The value of the data item referenced by data-name-1 and integer-2 is not restricted. For ANS85 only: Format 3. 14. Record descriptions following an input-output CD implicitly redefine this record and must describe a record of exactly 33 standard data characters. Multiple redefinitions of this record are permitted; however, only the first redefinition may contain VALUE clauses. The MCS will always reference the record according to the data descriptions defined in General Rule 26. General Rules. All Formats. 1. Table 2-1 indicates the possible contents of the data items referenced by data-name-10 for Format 1, data-name-3 for Format 2 and by data-name-6 for Format 3 (ANS85) at the completion of each statement shown. An "X" on a line in a statement column indicates that the associated code shown for that line is possible for that statement.Table 2-1: Communication Status Key ConditionTable 2-1: Communication Status Key Condition (continued) Format 1. 2. The input CD information constitutes the communication between the MCS and the program as information about the message being handled. This information does not come from the terminal as part of the message. 3. For each input CD, a record area of 87 contiguous standard data format characters is allocated. This record area is defined to the MCS as follows: * The SYMBOLIC QUEUE clausedefines data-name-1 as the name of an elementary alphanumeric data item of 12 characters occupying positions 1-12 in the record. * The SYMBOLIC SUB-QUEUE-1 clausedefines data-name-2 as the name of an elementary alphanumeric data item of 12 characters occupying positions 13-24 in the record. * The SYMBOLIC SUB-QUEUE-2 clausedefines data-name-3 as the name of an elementary alphanumeric data item of 12 characters occupying positions 25-36 in the record. * The SYMBOLIC SUB-QUEUE-3 clausedefines data-name-4 as the name of an elementary alphanumeric data item of 12 characters occupying positions 37-48 in the record. * The MESSAGE DATE clausedefines data-name-5 as the name of a data item whose implicit description is that of an integer of 6 digits without an operational sign occupying character positions 49-54 in the record. * The MESSAGE TIME clausedefines data-name-6 as the name of a data item whose implicit description is that of an integer of 8 digits without an operational sign occupying character positions 55-62 in the record. * The SYMBOLIC SOURCE clausedefines data-name-7 as the name of an elementary alphanumeric data item of 12 characters occupying positions 63-74 in the record. * The TEXT LENGTH clausedefines data-name-8 as the name of an elementary data item whose implicit description is that of an integer of 4 digits without an operational sign occupying character positions 75-78 in the record. * The END KEY clausedefines data-name-9 as the name of an elementary alphanumeric data item of 1 character occupying position 79 in the record. * The STATUS KEY clausedefines data-name-10 as the name of an elementary alphanumeric data item of 2 characters occupying positions 80-81 in the record. * The MESSAGE COUNT clausedefines data-name-11 as the name of an elementary data item whose implicit description is that of an integer of 6 digits without an operational sign occupying character positions 82-87 in the record. The second option can be used to replace the above clauses by a series of data-names which, taken in order, correspond to the data-names defined by these clauses. Use of either option results in a record whose implicit description is equivalent to the following: Implicit Description term nogloss| Phrase| 01 data-name-0. 02 data-name-1 PIC X(12). SYMBOLIC QUEUE 02 data-name-2 PIC X(12). SYMBOLIC SUB-QUEUE-1 02 data-name-3 PIC X(12). SYMBOLIC SUB-QUEUE-2 02 data-name-4 PIC X(12). SYMBOLIC SUB-QUEUE-3 02 data-name-5 PIC 9(06). MESSAGE DATE 02 data-name-6 PIC 9(08). MESSAGE TIME 02 data-name-7 PIC X(12). SYMBOLIC SOURCE 02 data-name-8 PIC 9(04). TEXT LENGTH 02 data-name-9 PIC X. END KEY 02 data-name-10 PIC XX. STATUS KEY 02 data-name-11 PIC 9(06). MESSAGE COUNT In the above, the information under "Phrase" is for clarification and is not part of the description. 4. The contents of the data items referenced by data-name-2, data-name-3, and data-name-4, when not being used must contain spaces. 5. The data items referenced by data-name-1, data-name-2, data-name-3, and data-name-4 contain symbolic-names designating queues, sub-queues, ..., respectively. All symbolic-names must follow the rules for the formation of system-names, and must have been previously defined to the MCS. 6. A RECEIVE statement causes the serial return of the "next" message or a portion of a message from the queue as specified by the entries in the CD. If during the execution of a RECEIVE statement, a message from a more specific source is needed, the contents of the data item referenced by data-name-1 can be made more specific by the use of the contents of the data items referenced by data-name-2, data-name-3, and in turn data-name-4. When a given level of the queue structure is specified, all higher levels must also be specified. If not all levels of the queue hierarchy are specified, the MCS determines the "next" message or portion of a message to be accessed. After the execution of a RECEIVE statement, the contents of the data items referenced by data-name-1 through data-name-4 will contain the symbolic-names of all the levels of the queue structure. 7. Whenever a program is scheduled by the MCS to process a message, that program establishes a run unit and the symbolic-names of the queue structure that demanded this activity will be placed in the data items referenced by data-name-1 through data-name-4 of the CD associated with the INITIAL clause as applicable. In all other cases, the contents of the data items referenced by data-name-1 through data-name-4 of the CD associated with the INITIAL clause are initialized to spaces. The symbolic-names are inserted or the initialization to spaces is completed prior to the execution of the first Procedure Division statement. The execution of a subsequent RECEIVE statement naming the same contents of the data items referenced by data-name-1 through data-name-4 will return the actual message that caused the program to be scheduled. Only at that time will the remainder of the CD be updated. 8. If the MCS attempts to schedule a program lacking an INITIAL clause, the results are undefined. 9. Data-name-5 has the format "YYMMDD" (year, month, day). Its contents represent the date on which the MCS recognizes that the message is complete. The contents of the data item referenced by data-name-5 are only updated by the MCS as part of the execution of a RECEIVE statement. 10. The contents of data-name-6 have the format "HHMMSSTT" (hours, minutes, seconds, hundredths of a second) and its contents represent the time at which the MCS recognizes that the message is complete. The contents of the data item referenced by data-name-6 are only updated by the MCS as part of the execution of the RECEIVE statement. 11. During the execution of a RECEIVE statement, the MCS provides, in the data item referenced by data-name-7, the symbolic-name of the communications terminal that is the source of the message being transferred. This symbolic move must follow the rules for the formation of system names. However, if the symbolic-name of the communication terminal is not known to the MCS, the contents of the data item referenced by data-name-7 will contain spaces. 12. The MCS indicates via the contents of the data item referenced by data-name-8 the number of character positions filled as a result of the execution of the RECEIVE statement. (See The RECEIVE Statement later in this chapter.) 13. The contents of the data item referenced by data-name-9 are set only by the MCS as part of the execution of a RECEIVE statement according to the following rules: * When the RECEIVE MESSAGE phraseis specified, then data-name-9 is set to one of the following: * If an end of group has been detected, the contents of the data item referenced by data-name-9 are set to 3; * If an end of message has been detected, the contents of the data item referenced by data-name-9 are set to 2; * If less than a message has been detected, the contents of the data item referenced by data-name-9 are set to 0. * When the RECEIVE SEGMENT phraseis specified, data-name-9 is set to one of the following: * If an end of group has been detected, the contents of the data item referenced by data-name-9 are set to 3. * If an end of message has been detected, the contents of the data item referenced by data-name-9 are set to 2. * If an end of segment has been detected, the contents of the data item referenced by data-name-9 are set to 1. * If less than a message segment is transferred, the contents of the data item referenced by data-name-9 are set to 0. * When more than one of the above conditions is satisfied simultaneously, the rule first satisfied in the order listed determines the contents of the data item referenced by data-name-9. 14. The contents of the data item referenced by data-name-10 indicate the status condition of the previously executed RECEIVE, ACCEPT MESSAGE COUNT, ENABLE INPUT, or DISABLE INPUT statements. The actual association between the contents of the data item referenced by data-name-10 and the status conditionitself is defined in Table 2-1. 15. The contents of the data item referenced by data-name-11 indicate the number of messages that exist in a queue, sub-queue-1,....The MCS updates the contents of the data item referenced by data-name-11 only as part of the execution of an ACCEPT statement with the COUNT phrase. Format 2. 16. The nature of the output CD information is such that it is not sent to the terminal, but constitutes the communication between the program and the MCS as information about the message being handled. 17. For each output CD, a record area of contiguous standard data format characters is allocated according to the following formula: (10 plus 13 times integer-2). * The DESTINATION COUNT clausedefines data-name-1 as the name of a data item whose implicit description is that of an integer without an operational sign occupying character positions 1-4 in the record. * The TEXT LENGTH clausedefines data-name-2 as the name of an elementary data item whose implicit description is that of an integer of 4 digits without an operational sign occupying character positions 5-8 in the record. * The STATUS KEY clausedefines data-name-3 to be an elementary alphanumeric data item of 2 characters occupying positions 9-10 in the record. * Character positions 11-23 and every set of 13 characters thereafter will form table items of the following description: * The ERROR KEY clausedefines data-name-4 as the name of an elementary alphanumeric data item of 1 character. * The SYMBOLIC DESTINATION clausedefines data-name-5 as the name of an elementary alphanumeric data item of 12 characters. Use of the above clauses results in a record whose implicit description is equivalent to the following (the information under "Phrase" is for clarification and is not part of the description): Implicit Description Phrase 01 data-name-0. 02 data-name-1 PIC 9(04). DESTINATION COUNT 02 data-name-2 PIC 9(04). TEXT LENGTH 02 data-name-3 PIC XX. STATUS KEY 02 data-name OCCURS integer-2 TIMES. DESTINATION TABLE 03 data-name-4 PIC X. ERROR KEY 03 data-name-5 PIC X(12) SYMBOLIC DESTINATION 18. During the execution of a SEND, ENABLE OUTPUT, or DISABLE OUTPUT statement, the contents of the data item referenced by data-name-1 will indicate to the MCS the number of symbolic destinations that are to be used from the area referenced by data-name-5. The MCS finds the first symbolic destination in the first occurrence of the area referenced by data-name-5, the second symbolic destination in the second occurrence of the area referenced by data-name-5... , up to and including the occurrence of the area referenced by data-name-5 indicated by the contents of data-name-1. If during the execution of a SEND, ENABLE OUTPUT, or DISABLE OUTPUT statement the value of the data item referenced by data-name-1 is outside the range of 1 through integer-2, an error condition is indicated and the execution of the SEND, ENABLE OUTPUT, or DISABLE OUTPUT statement is terminated. 19. It is the responsibility of the user to insure that the value of the data item referenced by data-name-1 is valid at the time of execution of the SEND, ENABLE OUTPUT, or DISABLE OUTPUT statement. 20. As part of the execution of a SEND statement, the MCS will interpret the contents of the data item referenced by data-name-2 to be the user's indication of the number of leftmost character positions of the data item referenced by the associated SEND identifier from which data is to be transferred. (See The SEND Statement later in this chapter.) 21. Each occurrence of the data item referenced by data-name-5 contains a symbolic destination previously known to the MCS. These symbolic destination-names must follow the rules for the formation of system-names. 22. The contents of the data item referenced by data-name-3 indicate the status condition of the previously executed SEND, ENABLE OUTPUT or DISABLE OUTPUT statement. The actual association between the contents of the data item referenced by data-name-3 and the status condition itself is defined in Table 2-1. 23. If, during the execution of a SEND, an ENABLE OUTPUT, or a DISABLE OUTPUT statement, the MCS determines that any specified destination is unknown, the contents of the data item referenced by data-name-3 and all occurrences of the data items referenced by data-name-4 are updated. The contents of the data item referenced by data-name-4 when equal to 1 indicate that the associated value in the area referenced by data-name-5 has not been previously defined to the MCS. Otherwise, the contents of the data item referenced by data-name-4 are set to zero. Format 2. 24. Table 2-2 indicates the possible content of the data item referenced by data-name-4 at the completion of each statement shown. An "X" on a line in a statement column indicates that the associated error key value shown for that line is possible for that statement.Table 2-2 : Error Key Values For ANS85 only: Format 3. 25. The input-output CD information constitutes the communication between the MCS and the program about the message being handled. This information does not come from the terminal as part of the message. 26. For each input-output CD, a recoard area of 33 contiguous character positions is allocated. This record area is defined to the MCS as follows: * The MESSAGE DATE clause defines data-name-1 as the name of a data item whose implicit description is that of an integer of 6 digits, without an operational sign, occupying positions 1-6 in the record. * The MESSAGE TIME clause defines data-name-2 as the name of a data item whose implicit description is that of an integer of 8 digits, without an operational sign, occupying positions 7-14 in the record. * The SYMBOLIC TERMINAL clause defines data-name-3 as the name of an elementary alphanumeric data item of 12 characters occupying positions 15-26 in the record. * The TEXT LENGTH clause defines data-name-4 as the name of an elementary data item whose implicit description is that of an integer of 4 digits, without an operational sign, occupying positions 27-30 in the record. * The END KEY clause defines data-name-5 as the name of an elementary alphanumeric data item of 1 character occupying position 31 in the record. * The STATUS KEY clause defines data-name-6 as the name of an elementary alphanumeric data item of 2 character occupying positions 32 and 33 in the record. The second option may be used to replace the above clauses by a series of data-names which, taken in order, correspond to the data-names defined by these clauses. Use of either option results in a record whose implicit description is equivalent to the following (the information under "COMMENT" is for clarification and is not part of the data description): Implicit Description Comment 01 data-name-0 02 data-name-1 PIC9(6). MESSAGE DATE 02 data-name-2 PIC9(8). MESSAGE TIME 02 data-name-3 PICX(12). SYMBOLIC TERMINAL 02 data-name-4 PIC9(4). TEXT LENGTH 02 data-name-5 PICX. END KEY 02 data-name-6 PICXX STATUS KEY 27. When a program is scheduled by the MCS to process a message, the first RECEIVE statement referencing the input-output CD with the INITIAL clause returns the actual message that caused the program to be scheduled. 28. Data-name-1 has the format "YYMMDD" (year, month, day). Its content represents the date on which the MCS recognizes that the message is complete. The content of the data item referenced by the data-name-1 is updated only by the MCS as part of the execution of a RECEIVE statement. 29. Data-name-2 has the formal "HHMMSSTT" (hours, minutes, seconds, hundredths of a second) and its content represents the time at which the MCS recognizes that the message is complete. The content of the data item referenced by data-name-2 is updated only by the MCS as part of the execution of the RECEIVE statement. 30. Whenever a program is scheduled by the MCS to process a message, that program establishes a run unit, and the symbolic name of the communication terminal that is the source of the message that invoked this program, is placed in the data item referenced by data-name-3 of the input-output CD associated with the INITIAL clause as applicable. This symbolic name must follow the rules for the formation of system-names. In all other cases, the content of the data item referenced by data-name-3 of the input-output CD associated with the INITIAL clause is initialized to spaces. The symbolic name is inserted, or the initialization to spaces is completed, prior to the execution of the first Procedure Division statement. 31. If the MCS attempts to schedule a program lacking an INITIAL clause, the results are undefined. 32. When the INITIAL clause is specified for an input-output CD and the program is scheduled by the MCS, the content of the data item referenced by data-name-3 must not be changed by the program. If this content is changed, the execution of any statement referencing cd-name-1 is unsuccessful, and the data item referenced by data-name-6 is set to indicate unknown source or destination, as applicable. (See General Rule 1.) 33. For an input-output CD without the INITIAL clause, or for an input-output CD with the INITIAL clause when the program is not scheduled by the MCS, the program must specify the symbolic name of the source or destination in data-name-3 prior to the execution fo the first statement referencing cd-name-1. After executing the first statement referencing cd-name-1, the content of the data item referenced by data-name-3 must not be changed by the program. If this content is changed, the execution of any statement referencing cd-name-1 is unsuccessful, and the data item referenced by data-name-6 is set to indicate unknown source or destination, as applicable. (See General Rule 1.) 34. The MCS indicates, through the content of the data item referenced by data-name-4, the number of character positions filled as a result of the execution of the RECEIVE statement. See the section The RECEIVE Statement later in this chapter.) As part of the execution of a SEND statement, the MCS interprets the content of the data item referenced by data-name-4 as an indication of the number of leftmost character positions of the data item referenced by the associated SEND identifier from which data is transferred. See the section The SEND Statement later in this chapter. 35. The content of the data item referenced by data-name-5 is set only by the MCS as part of the execution of a RECEIVE statement according to the following rules: * When the RECEIVE MESSAGE phrase is specified: * If an end of group has been detected, the content of the data item referenced by data-name-5 is set to 3. * If an end of message has been detected, the content of the data item referenced by data-name-5 is set to 2. * If less than a message is transferred, the content of the data item referenced by data-name-5 is set to 0. * When the RECEIVE SEGMENT phrase is specified: * If an end of group has been detected, the content of the data item referenced by data-name-5 is set to 3. * If an end of message has been detected, the content of the data item referenced by data-name-5 is set to 2. * If an end of segment has been detected, the content of the data item referenced by data-name-5 is set to 1. * If less than a message segment is transferred, the content of the data item referenced by data-name-5 is set to 0. * When more than one of the conditions is satisfied simultaneously, the rule first satisfied in the order listed determines the content of the data item referenced by data-name-5. 36. The content of the data item referenced by data-name-6 indicates the status condition of the previously executed DISABLE, ENABLE, PURGE, RECEIVE, or SEND statement. The actual association between the content of the data item referenced by data-name-6 and the status condition itself is defined in General Rule 1.
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