D Special Migration Cases
This appendix provides examples of special migration cases.
The following topics are addressed here:
Tables with Multiple Primary Keys
OWB tables are migrated to ODI data stores. In OWB, tables can have multiple primary keys. In ODI, data stores can have only one primary key. In the case of multiple primary keys, the first primary key is migrated as the primary key in ODI, and the others are migrated as alternate keys.
When this situation occurs, the following warning message is written to the migration utility log file:
{0}:{1} has multiple primary keys. Only one primary key is allowed in ODI, the redundant primary keys will be migrated as alternate keys.
Special Cases for Mappings
Some OWB mappings have different graph structures after they are migrated to ODI. The migration utility attempts to migrate OWB mappings to ODI as closely as possible, but in some cases the resulting ODI mappings may not correspond to the original OWB mapping structure.
The following special cases for mappings are addressed here:
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Multiple Operators Connected to Same Operator, Some with No Upstream Source
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Multiple Operators Connected to Same Operator, All with Different Upstream Operator
Two Operators Connected to Same Downstream Operator
The following figure shows an OWB mapping for which operators EMP and EXPRESSION are both connected to operator TGT_EMP through the same map attribute group INOUTGRP1. This is not allowed in ODI, because each input connector point in ODI can only be connected once.
The OWB mapping in the preceding figure is migrated to the ODI mapping in the following figure.
Multiple Operators Connected From and To Same Operator
The following figure shows an OWB mapping for which operators FILTER and EXPRESSION are both connected to operator TGT_EMP through the same map attribute group INOUTGRP1. This is not allowed in ODI.
During migration, the FILTER and EXPRESSION operators are chained together to ensure that only one is connected to TGT_EMP. As a result, the ODI mapping may be EMP > FILTER > EXPRESSION > TGT_EMP or EMP > EXPRESSION > FILTER > TGT_EMP.
The OWB mapping in the preceding figure is migrated to the ODI mapping in the following figure.
Lookup Operator Has a Constant as Input
The following figure shows an OWB mapping for which the Lookup operator has no upstream source operator, and is only connected from a constant.
The OWB mapping in the preceding figure is migrated to the ODI mapping in the following figure (DEP is the lookup table of the Lookup operator).
The constant operator CONSTANT in the OWB mapping is not migrated to any map component in ODI. Instead, the expression of the constant attribute is migrated, and that expression is set on the Lookup component.
For example, in OWB, if the expression of the attribute CONSTANT.OUTGRP1.NO is set to 5, and the lookup condition of LOOKUP_DEPT is OUTGRP1.DEPTNO = INGRP1.NO, then after migration the lookup condition of LOOKUP_DEPT in ODI is DEP.DEPTNO = 5.
Lookup Operators Have No Driver Table (Mapping Is Invalid)
The following figure shows an OWB mapping for which several Lookup operators are connected to operator TGT_EMP, but some of the Lookup operators have no upstream operators as driver tables. This mapping is invalid, but will also be migrated. All Lookup operators are chained together to ensure that only one is connected to TGT_EMP.
The OWB mapping in the preceding figure is migrated to the ODI mapping in the following figure.
Multiple Operators Connected to Same Operator, Some with No Upstream Source
The following figure shows an OWB mapping for which two operators are connected to the same operator TGT_EMP. The EXPRESSION operator has an upstream source operator, while the JOINER operator does not. Only one map component can be connected to TGT_EMP in ODI. As a result, the operator with no upstream source operator will lose the connection to TGT_EMP.
The OWB mapping in the preceding figure is migrated to the ODI mapping in the following figure.
Multiple Operators Connected to Same Operator, All with Different Upstream Operator
The following figure shows an OWB mapping for which two operators are connected to the same operator TGT_EMP. Both operators have an upstream operator. Only one map component can be connected to TGT_EMP in ODI. As a result, one operator will lose the connection to TGT_EMP.
The OWB mapping in the preceding figure is migrated to one of the ODI mappings in the following figures.
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