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Table of Contents
- Writing New Records
- Updating Existing Records
- Deleting a Record
- Shared Access
When records are written to a file for the first time, they are usually written
sequentially. Following execution of an FWRITE intrinsic, the logical
record pointer is positioned at the next sequential record in key sequence or
at the end-of-file marker if the record is the last in sequence.
Updating and deleting records also rely on pointer positioning. The logical and
physical record pointers are usually positioned by a read procedure, as
discussed in Chapter 5 "Reading File Data". Typically,
a read procedure precedes an update or delete procedure to verify that the
correct record has been found. Table 6-1 "Pointer
and Advance Flag Settings for Writing" specifies the advance flag and
pointer usage of each of the writing, updating, and deletion intrinsics.
Table 6-1 Pointer and Advance Flag Settings for Writing
| Intrinsic |
Reads Advance Flag |
Sets Pointer |
Sets Advance Flag |
Pointer Dependant |
| FREMOVE | no | both | no | yes |
| FUPDATE (keys unchanged) | no | none | yes | yes |
| FUPDATE(keys changed) | no | both | no | yes |
| FWRITE | no | both | no | yes |
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