Compaq COBOL AAQ2G1FTK - Manual (Page 7)

6 Processing Files and Records
6.1 Defining Files and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1
6.1.1 File Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–2
6.1.2 Record Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–8
6.1.3 File Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–13
6.2 Identifying Files and Records from Within Your Compaq COBOL
Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6–14
6.2.1 Defining a File Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–14
6.2.2 Specifying File Organization and Record Access Mode . . . . . . . . . . . . . 6–20
6.3 Creating and Processing Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–24
6.3.1 Opening and Closing Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–24
6.3.2 File Handling for Sequential and Line Sequential Files . . . . . . . . . . . 6–26
6.3.3 File Handling for Relative Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–29
6.3.4 File Handling for Indexed Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–32
6.4 Reading Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–37
6.4.1 Reading a Sequential or Line Sequential File . . . . . . . . . . . . . . . . . . . 6–37
6.4.2 Reading a Relative File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–38
6.4.3 Reading an Indexed File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–42
6.5 Updating Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–48
6.5.1 Updating a Sequential or Line Sequential File . . . . . . . . . . . . . . . . . . 6–48
6.5.2 Updating a Relative File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–50
6.5.2.1 Rewriting a Relative File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–50
6.5.2.2 Deleting Records from a Relative File . . . . . . . . . . . . . . . . . . . . . . 6–53
6.5.3 Updating an Indexed File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–55
6.6 Backing Up Your Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–60
7 Handling Input/Output Exception Conditions
7.1 Planning for the AT END Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–2
7.2 Planning for the Invalid Key Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–2
7.3 Using File Status Values and OpenVMS RMS Completion Codes . . . . . . . 7–3
7.3.1 File Status Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
7.3.2 RMS Completion Codes (OpenVMS) . . . . . . . . . . . . . . . . . . . . . . . . . . 7–5
7.4 Using Declarative USE Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–8
8 Sharing Files and Locking Records
8.1 Controlling Access to Files and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–1
8.2 Choosing X/Open Standard or Compaq Standard File Sharing and Record
Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8–3
8.3 Ensuring Successful File Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–4
8.3.1 Providing Disk Residency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–4
8.3.2 Using File Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–4
8.3.3 Determining the Intended Access Mode to a File . . . . . . . . . . . . . . . . . 8–6
8.3.4 Specifying File Access Using X/Open Standard File Sharing . . . . . . . . 8–6
8.3.5 Specifying File Access Using Compaq Standard File Sharing . . . . . . . 8–8
8.3.6 Error Handling for File Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–12
8.4 Ensuring Successful Record Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–16
8.4.1 X/Open Standard Record Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–17
8.4.2 Compaq Standard Record Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–18
8.4.3 Error Handling for Record Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–23
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