Relation between Category, SubCategory and CI Class

[snow_hard252]

Hi Community

I have couple of questions in Config and Asset management:

Though the cmdb_ci creation is driven by CI Class via the New interceptor in FUJI, I would like to understand the relationship between Category, Subcategory Fields on cmdb_ci and the particular CI Class.

Is the model_id the stitching field/attribute between the cmdb_ci and alm_asset tables , there by reflecting in Asset management and Configuration management?

Appreciate if some body can exemplify the above to questions.

Thanks

Hardy

[juancarlos_muro]

Hi Hardy,

Class is the table where the Configuration Item is stored.

For example, a record with class "cmdb_ci_linux_server" is stored in the table Linux Server. In ServiceNow CMDB follows a hierarchical approach, similar to inheritance in object oriented programming languages. The table [cmdb_ci_linux_server] extends from [cmdb_ci_server] which extends from [cmdb_ci_computer] which extends from [cmdb_ci_hardware] which extends from [cmdb_ci].

That way, linux servers will have their own fields plus the fields from each of those tables.

There is a lot of information about CMDB in our Wiki. The next one is a good introduction to CMDB:

-CMDB Classifications

http://wiki.servicenow.com/index.php?title=CMDB_Classifications

About Category, this is a calculated field.

In the definition of this field there is a dynamic filter that calculates the value of this field when a CI is created. The filter is "Get CMDB Item Category". This filter goes to the table "CMDB Categories [cmdb_categories]" and looks for the corresponding category and subcategory of the CI that is being created.

For example, if we are creating a linux server the filter will set category to "Hardware" and subcategory to "Computer" because there is an entry in "CMDB Categories [cmdb_categories]" with values "Name: cmdb_ci_linux_server, Category: Hardware, Subcategory: Computer".

Cheers,

Carlos

[snow_hard252]

Hi Juan,

Appreciate your time in detailing me out.

The answer will surely help, but OOB Categories and Subcategories may not be sufficient in real-time.

So as you said there is an underlying relation ship between CI Class and Category+ Subcategory.

I want to add new combinations into Category & Subcategory which will suite the requirements at hand.

Please let me know your thoughts if this could be done and suggest me.

Regards

[juancarlos_muro]

Hi Hardy,

Sure thing, you can add more combinations of   "Name / Category / Subcategory" to the table "CMDB Categories".

For that, go to https://<your-instance.service-now.com>/cmdb_categories_list.do and click New.

Keep in mind that ServiceNow won't let you add an entry for a class (Name) that already has an entry (ie, you can not add an entry for Linux Server because there is already one).

About Assets, you were in the good direction: model categories associate CI classes with Asset classes.

Those are the first words in the next Wiki article:

Model Categories - ServiceNow Wiki

Also very advised to read:

Creating New Models - ServiceNow Wiki

Best regards,

Carlos

[snow_hard252]

Hi Carlos,

Thanks for the clarifications..

I want to understand the relation between sys_class_name & cmdb_ci_class.

However I'm still trying to understand the exacts :

1) category field in cmdb_ci.do : how is it related to cmdb_categories

2) class field in cmdb_categories : how is it related to sys_class_name   of cmdb_ci

3) cmdb_model_category : how is the cmdb_model_category , cmdb_ci_class related to cmdb_categories

To add to this:

As per wiki , there should be a model category for each CI Class.

I presume all the table names beginning with cmdb_ci_* , represent CI Class, which are 364 CI Class types

But when I filter the cmdb_ci.list based on Class, I can see only 30 Class types

And when I filter the cmdb_model_category.list based on CI Class, I can see 118 CI Class types

So I'm trying to correlate the things but I'm missing few links.

Appreciate your inputs, and apologies if I'm asking something really wrong.

Thanks