Hi ALL i am running thru same issue.. My requirement is to run the batch every 15 mins and i ger error all the time that my

The Apex job named "Schedule Job1" is already scheduled for execution."

Below  is my code.

global class updateOpportunityStage implements Database.Batchable<sObject>,Schedulable{
global string query ;

global updateOpportunityStage(){

Query = 'Select Id,BigMachines__Status__c  from BigMachines__Quote__c' ;

}

global database.querylocator start(Database.BatchableContext BC){
return Database.getQueryLocator(query);    
}
    global void execute(SchedulableContext SC){
        updateOpportunityStage stg = new updateOpportunityStage();
        //String SCHEDULE_NAME = 'Process Quotes'; 
        //id cronid = System.schedule(SCHEDULE_NAME, '0 0 * * * ?', stg); 
        
       String sch = '0 15 * * * ?';
System.schedule('Schedule Job1', sch,stg);

  updateOpportunityStage stg2 = new updateOpportunityStage();
String sch2 = '0 15 * * * ?';
System.schedule('Schedule Job2', sch2, stg2);

        updateOpportunityStage stg3 = new updateOpportunityStage();
String sch3= '0 30 * * * ?';
System.schedule('Schedule Job3', sch3, stg3);

        updateOpportunityStage stg4 = new updateOpportunityStage();
String sch4 = '0 45 * * * ?';
System.schedule('Schedule Job4', sch4, stg4);

        
        
        
      //  System.abortJob(cronid);
//String cronStr =Datetime.now().addSeconds(10).format('s m H d M ? yyyy');
     //  System.schedule('Process Quotes', cronStr, stg);
        //System.abortJob(cronstr);
        
       /* String hour = String.valueOf(Datetime.now().hour());

String min = String.valueOf(Datetime.now().minute());

String ss = String.valueOf(Datetime.now().second());

String nextFireTime = ss + ' ' + min + ' ' + hour + ' * * ?';

system.schedule('Start me once', nextFireTime, stg); */
        database.executebatch(stg);
        
    }

global void execute(Database.BatchableContext BC, List<sObject> scope){

     
        Set<id> liOppIds = new Set<id>();
//List <Opportunity> oppList = new List<Opportunity>() ;
for(sObject s : scope){

BigMachines__Quote__c quote = (BigMachines__Quote__c)s;
System.debug('Adil'+quote);
if(quote.BigMachines__Status__c == '*unison*' && quote.BigMachines__Is_Primary__c == true)
liOppIds.add(quote.BigMachines__Opportunity__c);

}


//query all the opportunities in a single query
List<Opportunity> opp = new List<Opportunity>();
opp = [select id, StageName from Opportunity where id in :liOppIds and stagename != 'Closed Won'];
for ( Opportunity opps : opp)
{
opps.StageName = 'Closed Won' ; 
}
//update all opportunities in a single DML
if(opp.size() > 0)
update opp;
 
    }
  global void finish(Database.BatchableContext BC){}  

}

 thanks