While chasing an error to which only applied to join type stages, I thought it might be nice to identify what the InfoSphere Information Server DataStage / QualityStage are.  There are three of them, as you can see from the picture above, which are the:

• Join Stage,
• Lookup Stage,
• And, Merge Stage.

All three stages that join data based on the values of identified key columns.

Related References

IBM Knowledge Center, InfoSphere Information Server 11.7.0, InfoSphere DataStage and QualityStage, Developing parallel jobs, Processing Data, Lookup Stage

• https://www.ibm.com/support/knowledgecenter/SSZJPZ_11.7.0/com.ibm.swg.im.iis.ds.parjob.dev.doc/topics/c_deeref_Lookup_Stage.html

IBM Knowledge Center, InfoSphere Information Server 11.7.0, InfoSphere DataStage and QualityStage, Developing parallel jobs, Processing Data, Join Stage

• https://www.ibm.com/support/knowledgecenter/SSZJPZ_11.7.0/com.ibm.swg.im.iis.ds.parjob.dev.doc/topics/c_deeref_Join_Stage.html?view=kc

IBM Knowledge Center, InfoSphere Information Server 11.7.0, InfoSphere DataStage and QualityStage, Developing parallel jobs, Processing Data, Merge Stage

• https://www.ibm.com/support/knowledgecenter/SSZJPZ_11.7.0/com.ibm.swg.im.iis.ds.parjob.dev.doc/topics/c_deeref_Merge_Stage.html