CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY:insertAccount: System.LimitException: Attempted to schedule too many concurrent batch jobs in this org (limit is 5).

Only 800 got inserted out of 20K how to solve this issue?

- Batch Apex can have 5 concurrent (simultaneous) jobs running in parallel.
- That is, explicitly, the number of Batch Apex jobs whose status in the AsyncApexJob table are 'Processing' or 'Preparing'.
- A job is not executing when in Queued or any other status.

- Scheduling more than 5 Batch Apex jobs returns the error "Attempted to schedule too many concurrent batch jobs in this org"
- You may sometimes receive a Developer script exception e-mail when this limit is reached, but not always. (This is also by design).

- You may attempt to use the following code sample to avoid encountering this limit, particularly if the batch is executed in a scheduled class. 

- Count how many current jobs are being executed.
- This information is stored in the AsyncApexJob table.
- Before calling the Database.executebatch() method within a scheduled class, you should try something like:

//check if there are 5 active batch jobs
if ([SELECT count() FROM AsyncApexJob WHERE JobType='BatchApex' AND (Status = 'Processing' OR Status = 'Preparing')] < 5]){
   Database.executeBatch(batchClassInstance);
} else {
   //schedule this same schedulable class again in 30 mins
   nameOfYourSchedulableClass sc = new nameOfYourSchedulableClass();
   Datetime dt = Datetime.now() + (0.024305); // i.e. 30 mins
   String timeForScheduler = dt.format('s m H d M \'?\' yyyy');
   Id schedId = System.Schedule('MatrixRetry'+timeForScheduler,timeForScheduler,sc);
}

- In the same 'else' clause you can send an e-mail to yourselves so you're notified that the job will run a bit later than normal.

Note:

- You have can have more than 5 scheduled classes that will call Database.executeBatch() in a Queued status 

I found this where exactly I have to embed this code in my batch class :

global class InsertAccounts implements Database.Batchable<sObject> {
//map of contactid - contact
Map<Id, Contact> contactMap = new Map<Id, Contact>();
global InsertAccounts(Map<Id, Contact> contacts) {
ContactMap = contacts;
}
global Database.QueryLocator start(Database.BatchableContext BC) {
return DataBase.getQueryLocator([SELECT Id,FirstName, LastName,AccountId, Name FROM Contact WHERE AccountId = null AND Id IN : contactMap.keySet()]);
}

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

List<Account> accounts = new List<Account>();
Map<String,Contact> mapContacts = new Map<String,Contact>();
for (Contact con : scope){

Account acc = new Account();
acc.Name = con.Name;
accounts.add(acc);

mapContacts.put(con.Name, con);
}
if(accounts.size() > 0)
insert accounts;

List<Contact> conts = new List<Contact>();
for(Account acc : [Select Id, Name From Account Where Name IN : mapContacts.keySet()]) {
if(mapContacts.containsKey(acc.Name)) {

mapContacts.get(acc.Name).AccountId = acc.Id;
conts.add(mapContacts.get(acc.Name));
}
}
if(conts.size() > 0)
update conts;
}
global void finish(Database.BatchableContext BC) {
}
}

Please let me know