Final answer:
When changing the custom field's data type, it is crucial to consider whether the field is mapped for lead conversion and to understand that not all data type changes are supported. Care must be taken to ensure compatibility and to preserve data integrity.
Step-by-step explanation:
When changing a custom field's data type, there are two important considerations. First, changing a custom picklist to a multi-select picklist may cause data loss. This is because the values in the original picklist may not be compatible with the new multi-select picklist. Second, a user can change the data type of a custom field that is mapped for lead conversion. This means that if a custom field is being used in the process of converting leads, the data type change should be done carefully to ensure that the conversion process continues to work correctly.
For (b), while it's possible to change the data type of a field that is mapped for lead conversion, it's essential to recognize that the new data type must be compatible with the existing mappings to ensure a seamless transition and avoid disruption in the lead conversion process. For (c), it's important to note that not all custom field data types can be directly converted into another; some changes may not be supported or might require intermediary steps to prevent data loss or functional issues.
Changing the data type of a custom field can have a significant impact on your data's integrity and on system functionality, so it's crucial to consider these aspects before making any changes. It may involve data migration, system testing, and updates to related workflows, reports, or processes that utilize the field. Salesforce, the context for these data field considerations, provides extensive documentation on these limitations and processes, which should be reviewed thoroughly beforehand.