Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved


Chapter 3 Managing IDMS/DB Data Definitions : Mapping Considerations

Mapping Considerations
In choosing an optimal access path, it is critical that the person defining IDM table definitions be familiar with the structure of the CA‑IDMS database.
Effects of Record Selection
Consider the following points when selecting CA‑IDMS records:
Determine the data you require and an optimal access path to retrieve that data. Create an IDM table definition to match your requirements or review existing definitions for a match. Do not use existing definitions if they contain extra records for the following reasons:
Unless the Show? field on the Set Connections screen is set to Y, when more than one record is defined in an IDM table definition, the Gateway returns data only when all record types exist in the specified sets. For example, if the EMPLOYEE and COVERAGE records are defined in an IDM table, only EMPLOYEEs that have COVERAGE are returned. EMPLOYEEs that do not have COVERAGE cannot be retrieved with this definition. Refer to Task G  Verify the Access Path for more information on the Show? field.
When the extra member records do exist, they all must be retrieved and returned to TIBCO Object Service Broker since the table definition requested them.
When the required access path contains two CALC records, be sure to examine your application retrieval needs. If most retrieval requests specify a value for the CALC key of both CALC records, consider which record should come first in the access path.
Consider a table that has OFFICE (CALC) and EMPLOYEE (CALC) defined in an access path. To find a specific EMPLOYEE in a specific OFFICE, the Gateway CALCs to the OFFICE record and searches the OFFICE-EMPLOYEE set until the specified EMPLOYEE is found. If the EMPLOYEE record were the first in the access path, the Gateway could CALC to the specified EMPLOYEE and do an OBTAIN OWNER to retrieve the OFFICE.
Ensure VIA records are accessed through CALC owner records to avoid area sweeps. VIA records that have system-owned indexes can be accessed by that index.
Effects of Element Selection
Consider the following points when selecting elements:
Include IDMS/DB elements that are part of an index or set in the table definition. If selection criteria are specified for this type of field, the Gateway can use the field for positioning and walk the set from that point. Refer to Accessing TIBCO Object Service Broker IDM Tables for more information.
The number of elements that you select as fields from each record in the table definition is used by the Gateway to determine whether a STORE should be done for that record when you issue an INSERT statement. Refer to Insert Processing for more information.

Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved