In most cases, a community certificate acts as a supporting document for obtaining a caste certificate. However, there are alternative ways to get your caste certificate if you don't have a community certificate.

Each state in India has its own rules regarding caste certificate issuance. Look for the official website of your state's revenue department or backward classes welfare department. These websites might outline the documents required for obtaining a caste certificate and might mention alternatives to a community certificate.

Visit your local Tehsildar office or the office that issues caste certificates in your area. They can clarify the specific requirements and guide you on alternative documents you can provide as proof of caste.

Some possible alternatives to a community certificate include:

Your school leaving certificates (from 10th and 12th standard) might mention your caste if it was declared at the time of admission.

Ancestral ration cards mentioning your caste can be considered as proof.

Land ownership documents mentioning the caste of the landholder (usually your parents or grandparents) might be helpful.

In some cases, you might be able to submit a sworn affidavit (notarized statement) declaring your caste based on your knowledge and family history.

A "Sangam Certificate" is not a commonly required document for admission to a BCA (Bachelor of Computer Applications) program. It is possible you might have misunderstood a requirement or received outdated information.

• Class 10th and 12th Mark Sheets: These are the most crucial documents for admission to any undergraduate program, including BCA.
  
  

• Entrance Exam Scores (if applicable): Some colleges might require entrance exam scores for admission to BCA programs. Check the specific admission requirements of the colleges you are interested in.
  
  

• Migration Certificate (if applicable): If you are applying to a college in a different state from your higher secondary education board, you might need a migration certificate.
  
  

• Character Certificate: Some colleges might ask for a character certificate from your previous institution.
  
  I hope it helps!