Error when trying to enable cube MV query rewrite

Question

Hi
I'm facing a problem when trying enable query rewrite on the cube materilized view, see below
Invalid Metadata Objects:
Invalid Object "ACCOUNTING.APP_CUBE": "XOQ-01957: The cube has REWRITE MVs and also contains either a ragged or skip-level hierarchy. The hierarchy is "ACCOUNTING.MACHINE.MACHINES"."
As far as I can tell the dimension should not have ragged or skip-level hierarchy as I understand it (having just read up on them now). The dimension only has two levels ALL_MACHINES and MACHINE. The mapping points to a table that has just 1 column the machine_key which has 8 just rows. This joins with a fact table that has just these 8 distinct values in it (and no NULLS).
Am I missing something obvious?
Thanks
Simon

Answer 1

Each 11g hierarchy has two properties that can be seen in the XML template for the dimension.
IsSkipLevel
IsRagged
For example
<LevelHierarchy
Name = "MACHINES"
IsSkipLevel = "True"
IsRagged = "True">
If you do not see them, then the default is False.
You should think of these properties as 'constraints' in the RDBMS sense. For example, if you say
IsSkipLevel = "False"
then the system will interpret this as a constraint that says that the hierarchy is not skip level -- i.e. all parents are always exactly one level above their children. This constraint is validated during dimension load (or, more precisely, dimension COMPILE). If you say it is not skip level and the server finds that it is skip level, then you will get an XOQ-01713 error during the load. If, on the other hand, you say
IsSkipLevel = "True"
then the system will interpret this as no constraint, so it will not check during load. Note that this does not say that there are skip levels in the hierarchy, it just says that the server will not check for skip levels. It is similar to an IS NOT NULL constraint on a column -- If the constraint is there then you can be sure that there are no NULLs; if it is not there, then there may or may not be NULLs.
The double negative implied in the XML property name is unfortunate -- a better name would have been something like "EnableNoSkipLevelConstraint = True", but the choice was made and backwards compatibility requirements makes it hard to change now.
Your specific error, XOQ-01957, is saying that the MACHINE hierarchy of the MACHINES dimension is marked as IsSkipLevel = "True" or IsRagged = "True". (It is probably both.) In other words the skip level and ragged constraints are not enabled on the hierarchy. To fix this you should flip the two properties to False in the XML and recreate the dimensions. Unfortunately you cannot change the properties directly in AWM 11.1 since AWM tries to manage the properties automatically for you. But there are times, like, this, when things go wrong.