PowerExchange Interfaces for PowerCenter

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Configuring Lookups for IMS

You can use keys to retrieve data efficiently from IMS databases. PowerExchange enables you to build Concatenated Key (CCK) fields in the data map. Concatenated Key (CCK) fields enables PowerExchange to construct a fully-qualified Segment Search Argument (SSA) thereby improving IMS database search efficiency.

Fields specified in the Lookup condition transformation attribute are used by PowerExchange to create the Segment Search Argument (SSA). In order for a field to be used in the SSA, it must be marked as a key in the IMS source or target definition in Designer.

To provide search keys for IMS database lookups, use the following types of fields in the Lookup condition transformation attribute:

Concatenated Key (CCK) fields.
Specify these fields as keys in the IMS source or target definition and use them in the Lookup condition attribute. The use of CCK fields results in the most efficient search of the IMS database.

Key fields.
Specify these fields as key in the IMS source or target definition and use them in the Lookup condition attribute. You can specify either the CCK field or the key field for the desired segment as both will exist in the IMS source or target definition. If the segment is not the root, a combination of both CCK fields and key fields will likely be needed in the Lookup condition.

Search fields defined in the IMS Database Definition (DBD).
Specify these as keys in the IMS source or target definition and use them in the Lookup condition attribute. If the segment does not have a key, IMS can still scan the IMS segments by using an IMS search field. This type of search call is not as efficient as a keyed search with CCK fields or key fields. Assuming the root segment is keyed, include its CCK field with the search fields to limit the amount of data IMS scans and therefore the impact on the database.

Non-key or non-search fields.
The least efficient search method is to mark non-key fields or non-search fields as keys in the IMS source or target definition and in the Lookup condition attribute. This causes a scan of the IMS database to be done in order to find a match. This can adversely affect your IMS operational system and therefore should be avoided.

You can limit the amount of the database that will be scanned by specifying as many CCK and key fields as possible. If you use Search fields, include as many CCK fields as possible and, at minimum, the root CCK field. Only use non-key or non-search fields as a last resort.

For more information about creating CCK fields in IMS data maps, see the PowerExchange Navigator User Guide
.

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Table of Contents

PowerExchange Interfaces for PowerCenter

PowerExchange Interfaces for PowerCenter

Configuring Lookups for IMS

Configuring Lookups for IMS