Interview Questions on Batch Apex In salesforce

1.What are the soql limitations in apex?
Ans: Total number of records retrieved by SOQL queries-50,000

2.What are the transaction limitations in apex?
Ans: Each execution of a batch Apex job is considered a discrete transaction.
For example, a batch Apex job that contains 1,000 records and is executed without the optional scope parameter from Database.executeBatch is considered five transactions of 200 records each.
The Apex governor limits are reset for each transaction.
If the first transaction succeeds but the second fails, the database updates made in the first transaction are not rolled back.

3.What is the need of batch apex?
Ans: By using Batch apex classes we can process the records in batches in asynchronously.

4.What is Database.Batchable interface?
Ans: The class that implements this interface can be executed as a batch Apex job.

5.Define the methods in batchable interface?
Ans:
Start:
global Database.Querylocator start (Database.BatchableContext bc){}
Execute:
global void execute(Database.BatchableContext bc,List <p>){}
Finish:
global void finish(Database.BatchableContext bc) {}

6.What is purpose of start method in batch apex?
Ans: It collect the records or objects to be passed to the interface method execute.

7.What is the Database.QueryLocator?
Ans: If we use a Database.QueryLocator,
the governor limit for the total number of records retrieved by SOQL queries is bypassed. (Default 50,000 It allow up to 50 million records).

8.What is the iterable<Sobject>?
Ans: If you use an iterable,
the governor limit for the total number of records retrieved by SOQL queries is still enforced.

9.What is the use of execute method?
Ans: Contains or calls the main execution logic for the batch job.

10.How many times execute method is called?
Ans: Execute method is called for  each batch of records.

11.What is the scope of execute method?
Ans: The maximum value for the optional scope parameter is 2,000

12.Can we call callouts from batch apex?
Ans: Yes we can call.

13.Can we call another batch apex from batch apex?
Ans: Yes you can call a batch apex from another batch apex .Either in start method or in finish method you can call other batch

14.How many callouts we can call in batch apex?
Ans: Batch executions are limited to one callout per execution.

15.Batch is synchronous or Asynchronous operations?
Ans: Asynchronous operations.

16.What is the maximum size of the batch and minimum size of the batch ?
Ans: The default batch size is 200 records. min?
max?

17.What is the Database.BatchableContext?
Ans: BatchableContext Interface is Represents the parameter type of a batch job method and
contains the batch job ID. This interface is implemented internally by Apex.

18.How to track the details of the current running Batch using BatchableContext?
Ans: You can check the AsyncApexJob.Status using the JobId from the Database.BatchableContext.

19.How many batch jobs can be added to queue?
Ans: Queued counts toward the limit of 5.

20.What is Database.State full interface?
Ans:To maintain variable value inside the Batch class, Database.Stateful is used.

21.What is Database.AllowCallouts?
Ans:
To use a callout in batch Apex, you must specify Database.AllowsCallouts in the class definition. For example:
global class SearchAndReplace implements Database.Batchable<sObject>,
   Database.AllowsCallouts{
              //Business logic you want by implementing Batchable interface methods
}
Callouts include HTTP requests as well as methods defined with the webService keyword.

22.What is AsyncApexJob object?
Ans: AsyncApexJob is Represents an individual Apex sharing recalculation job.
Use this object to query Apex batch jobs in your organization.

23.When a BatchApexworker record is created?
Ans: For each 10,000 AsyncApexJob records, Apex creates one additional AsyncApexJob record of type BatchApexWorker for internal use.