Bulk Addition Mode for Vision

This section includes the following:

When Vision writes a record to a file, its normal algorithm is to first add the record, then add the primary key, then add the first alternate key and so on until all the keys have been added. This is the algorithm one expects and is generally required to correctly support the WRITE verb.

Vision also has another technique that it can use to add records to a file. This technique does not write the keys to the file when it adds the record. Instead, it adds many records to the file first, then it gathers all the primary keys for those records and adds them, then it gathers all the first alternate keys and adds them and so on. By adding many keys at once, Vision can be much more efficient in its handling. This has two benefits:

1. The time it takes to add a large number of records using this technique is generally much smaller than using the normal technique; and
2. The resulting file is more efficiently organized, with all of the blocks associated with a particular key near each other on disk.

This technique of adding records to a file is called bulk addition mode. It is available only for Vision files. It may be used with any format Vision file.

You can use bulk addition mode in your programs. This is most useful in programs that add a large number of records to a file at once. It is less useful in programs that do operations other than WRITE on a file, or programs that do not write many records. Some typical applications for bulk addition mode are:

• Programs that load externally supplied data into a file. For example, a program that adds to an indexed file from the data contained in a sequential file.
• File conversion programs, such as programs that change a record format. These programs read from one file and write to a new one.
• Archiving programs.
• Programs that post transactions to permanent log files.

While bulk addition mode has fairly specialized uses, its benefits are high in these cases.

Bulk addition mode can provide substantial performance improvements over other techniques, including MASS-UPDATE mode. These improvements become more noticeable as the file grows and in files with a large number of alternate keys. For files with few records, bulk addition mode can be slightly less efficient than the normal WRITE technique.

Using bulk addition affects some of the standard COBOL file handling rules. These are described separately.