Commitment control is by default enabled in IBM DB2 since the following statement cannot update a file

update libname/filename set fld1 = 'test' where id = 1;.

You need to add with NC to the end of the above statement to disable the commitment control and commit the update operation on the table immediately.

update libname/filename set fld1 = 'test' where id = 1 with NC;

For using commitment control you need to enable journalling on the files first. You can follow the below steps to enable the journalling of files.

1. CRTJRNRCV: Create a journal reciever named jrnrcv0001 using this command.
   CRTJRNRCV JRNRCV(libname/JRNRCV0001)
2. CRTJRN: Create a journal named JRN0000001 and attach the journal receiver JRNRCV0001 using this command.
   CRTJRN JRN(libname/JRN0000001) JRNRCV(libname/JRNRCV0001)
3. STRJRNPF: Start journalling of files using a journal JRN0000001.
   STRJRNPF FILE(libname/filename) JRN(JRN0000001) IMAGES(*AFTER)

Once the journalling is started on files and then if you perform any update to this file through your program, you must either commit or roll back the update before your program ends. If you do not do this then the lock on the file will remain present after the program ends. You can use COMMIT command to commit the changes and ROLLBACK command to roll back the last commit or simply rollback call for the operation done so far that were not yet committed.