Question

Although MMS-ID is the primary identifier in Alma, I want to use a local control number as identifier.

Answer

You can use MARC-21 field 009 with the following configuration:

Step 1: configuring 009 as local control number
Configurations --> Resources --> Control Number

Mandatory Parameters:
Sequence Name
Method: Prefix + Sequence
Prefix: add the prefix that should be added to your sequence
Next Sequence: enter the next resp. first number the sequence should start
Padding: number of digits

Step 2: check that 009 index is activated.

Configurations --> Resources --> Indexes
 

Step 3: Add sequence to task

Configurations --> Resources --> Metadata Configuration --> MARC21 Bibliographic --> Normalization Processes --> Marc21 Bib normalize on save --> Task List

Add Task:

Task Parameters:

Sequence Name: add the name according to Step 1.

Step 4: Additionally you should create a MARC21 Field 035 from 009. You will probably need it e.g. for matching records during import etc.
To achieve this add a second task:

Task Parameters:

This task will then copy 009 to 035$$a with an ISIL-prefix (AT-OBV)

Step 5: To ensure that an already existing control number can not to be duplicated, when a new record is created, add the following validation exception:

Configurations --> Resources --> Metadata Configuration --> MARC21 Bibliographic --> Validation

 Task Parameter:

Add the corresponding message in the Validation Exception Profile List:

Configurations --> Resources --> Metadata Configuration --> MARC21 Bibliographic --> the Validation Exception Profile List

At MarcXML Bib Metadata Editing On Save click "Edit"

Click "Add Validation Severity Exception"

Additional Information:

As a result of all these steps you get a controlfield 009 AC... and a datafield 035$$a prefixed by ISIL-Code when saving a record in Metadata Editor.

If you duplicate the record and try to save it the following message appears:

Now Alma prohibits to save a second record with a preallocated 009.