Filippo - File performance is affected if you re-type Text to Category when there are more than roughly 200 unique values in a field. You CAN force Omniscope to do this, but first you should turn off the file setting that governs this performance-related internal re-typing:

Settings >Advanced file settings > untick Auto convert text fields

Then go to Data > Manage Fields and re-type the field you want to switch from Text to Category. Omniscope will warn you, but will apply the change up to the limits of your machine.

Yesterday, I forced Categorization of 34,000 client names in a file with 120,000 rows on a 32-bit machine with 2 GB RAM and MS Outlook open alongside...needless to say, performance was not great, but it DID work.

Hi tjbate,

Thank you very much for your help...I've just tried and it works!

May be you can give me a further advice...My problem is that, once I 've groupped by security ID (or for example by client in your case), my boss want to know whic are the most populated groups. In other words I would like to show and extract the group with the higest number of security ID (or clients in your case).
Do you think it would be possible?
Basically the problem is that, once you' ve groupped, you can't sort by one other field.
Many thanks again

Filippo

Filippo - Add a Formula Field: =Recordcount(Subset[Security ID]). This will tell you how many rows have the same Security ID. Sort on this field to rank the values. You can also use the Aggregation drop-down in a Table View to collapse all the rows with the same Security ID (you can even do this if you leave [Security ID] typed as Text rather than force Categories as above). If you use Aggregation, because you are going to apply Aggregation to the results of this formula, you need to set the Aggregation function for the formula field to be Formula result MEAN (not SUM!). This prevents double counting of records when aggregation is applied. Then determine what other fields to display in the aggregated View, and set their Aggregation functions to sensible things, or to none. If you have done this correctly, the sortable formula field should show the same row count as the Aggregated row count on the far left of the Aggregated Table View.