ACCESS MODE Clause - Format 4 - Transaction Files
IBM Extension
IBM Extension
End of IBM ExtensionACCESS MODE Clause - Format 4 - Transaction Files >>-ACCESS--+------+--+----+--+-SEQUENTIAL--| Rel Key |-+------->< '-MODE-' '-IS-' '-DYNAMIC--| Rel Key |----' Rel Key |--RELATIVE--+-----+--+----+--data-name-4-----------------------| '-KEY-' '-IS-'
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- ACCESS MODE IS SEQUENTIAL
- Can be specified for all three kinds of files.
- Sequential
- Records in the file are accessed in the sequence established when the file was created or extended (arrival sequence).
- Relative
- Records in the file are accessed in the ascending sequence of relative record numbers of existing records in the file.
- Indexed
- Records in the file are accessed in the sequence of ascending record
key values according to the collating sequence of the file.
IBM Extension
IBM Extension When using an externally described file, if the DDS keyword DESCEND is used when the field is specified as a key field, the records in the file are accessed in the sequence of descending record key values within the index. Either the DESCEND keyword, or the ASCEND keyword (if DESCEND is not specified) appears under the heading RETRIEVAL in a comment table in the COBOL source program listing. End of IBM Extension
End of IBM Extension
- ACCESS MODE IS RANDOM
- Can be specified for relative and indexed files only. Also, ACCESS MODE
IS RANDOM must not be specified for file names specified in the USING or GIVING
phrase of a SORT or MERGE statement.
- Relative
- The value placed in a relative key data item specifies the record to be accessed.
- Indexed
- The value placed in a record key data item for the current key of reference specifies the record to be accessed.
- ACCESS MODE IS DYNAMIC
- Can be specified for relative and indexed files only.
- Relative
- Records in the file may be accessed sequentially or randomly, depending on the form of the specific input-output request.
- Indexed
- Records in the file may be accessed sequentially or randomly, depending on the form of the specific input-output request.
