Creating SFS files

You can create SFS files with entry-sequenced (sequential), relative, or clustered formats. You can create each of the three SFS file types by using CICSSDT commands. Files can also be created programmatically. These three formats differ in the organization of their records:

• Records in entry-sequenced, or sequential, files are organized by their entry sequence numbers (ESNs), which describe the order in which the records were inserted in the file.
• Records in relative files are organized by their relative slot numbers (RSNs), which describe the position of each record in an array of record slots.
• Records in clustered files are organized in a tree structure based on the value of the key field or fields of the primary index.

Figure 1 shows sample records from each of the three SFS file types.

Figure 1. Sample records for SFS file types

• The MerchandiseOrders file is an entry-sequenced file. Each record represents an order placed. The record is inserted into the file chronologically, as each order is taken. The physical arrangement of records provided by entry-sequenced files is optimal for applications needing chronological access to information.
• The Inventory file is a relative file that stores information about stock items for a company. The records are organized by stock item number. The value of the StockNum field contains the RSN for records in this file. Applications can directly access inventory records using this number.
• The Accounts file is a clustered file. Its records are physically ordered according to the value of the customerName and customerAddress fields.

Table 1 summarizes the differences between the three types of SFS files.