Instead of always creating the same job that auto drops, you should create this job once for all and run it whenever you need.
To do so, create it as disabled with auto_drop=FALSE, and to run it just call the dbms_scheduler.run_job procedure.
DBMS_SCHEDULER.CREATE_JOB(job_name => 'export',
JOB_ACTION => 'exp tvm/tvm file=/home/srl/export/dump/backup'||'_'||to_char(sysdate,'DDMMYYHHMI')||'.dmp log=/home/srl/export/log/backup'||'_'||to_char(sysdate,'DDMMYYHHMI')||'.log',
enabled => FALSE,
auto_drop => FALSE
The 'export' job will peacefully stay as disabled. Whenever you need to run it, just call the run_job procedure:
CREATE OR REPLACE PROCEDURE run_export
DBMS_SCHEDULER.run_job(job_name => 'export');
Now, about your export not working, do you get an error or nothing happens?
Can you provide the output of the following query:
SELECT job_name, STATUS, ADDITIONAL_INFO
WHERE upper(job_name) = 'EXPORT';