Converting database types

If the characteristics of your applications have changed over a period of time, performance might be improved by changing to another DL/I access method.

DL/I access methods (or types of databases) are typically chosen based on such variables as:

• The type of processing you needed to do (sequential, direct, or both)
• The volatility of your data

Assuming that you have decided to change access methods, this topic tells you:

• Given your existing DL/I access method, what things you need to change to convert to a different DL/I access method
• How to do the conversion

The reorganization utilities described in related topics can be used to change DL/I access methods among the HISAM, HDAM, and HIDAM access methods. One exception to this is that HDAM cannot be changed to HISAM or HIDAM unless HDAM database physical records are in root key sequence. This exception exists because HISAM and HIDAM databases must be loaded with database records in root key sequence. When the HD Reorganization Unload utility unloads an HDAM database, it unloads it using GN calls. GN calls against an HDAM database unload the database records in the physical sequence in which they were stored by the randomizing module. This will not be root key sequence unless you used a sequential randomizing module (one that put the database records into the database in physical root key sequence).