I needed to change existing single value lookup to be multi-valued lookup, so I deleted old attribute and re-created new as multi-valued but i don't see any data I previously had for the same attribute id.
Release : 15.6.1
Component : CA PPM SAAS STUDIO
Customer had a custom attribute on Change Request object which is Lookup type and new requirement from business users is to make it as Multi-valued lookup.
Admin went ahead and deleted an existing attribute and re-created new as multi-valued with same attribute id in hope that data from previous attribute will remain in tact but this is not correct, the moment you delete an attribute it is completely dropping that column from the table and any data in it. Your only option if the requirement to retain old data to be transferred to new attribute is to create new attribute in addition to old one and using GEL script to copy data from old attribute to new.
Things to be aware of if you were to go with that approach: Multi-Valued attributes are stored in different table (ODF_MULTI_VALUED_LOOKUPS) and each value stored for an instance will have a separate line, for example if particular instance have 2 values selected for multi-valued attribute you will expect to see 2 lines in the table I mentioned above.