INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10

If a cursor uses a multi column index, where the 1st field is
the filter for the cursor and the
second field is updated by an UPDATE inside the cursor loop, and
the updated second field makes
the index key appear after the latest fetched row, the cursor
will keep picking up the updated keys
and loop forever until some other condition occurs (eg. the
value of field 2 becomes truncated
and matches already present values).

The problem doesn't occur if:
1- the table has a second index on the 1st field only
2- the cursor is for update (update uses CURRENT OF )

Having the database with or without logging makes no difference
but it may worth checking this is the case.
Isolation level doesn't affect the result (which should be
expected as it all happens inside the same session/application).

According to the documentation

http://www-01.ibm.com/support/knowledgecenter/SSGU8G_12.1.0/com.
ibm.sqlt.doc/ids_sqt_330.htm?lang=en

"When only one program is using a database, the members of the
active set cannot change"

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* USERS AFFECTED:                                              *
* Informix 11.70, 12.10                                        *
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* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
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* RECOMMENDATION:                                              *
* See Problem Conclusion                                       *
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not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

08.01.2016
28.06.2016
28.06.2016