The SQL Server Agent by default only keeps 1000 rows of history for all jobs. There is also a limitation for each job to keep only 100 rows each. These rows do not only include the a row for the entire job, but the rows for each step in the job also. These rows can quickly get filled leaving you in the dark when you need to troubleshoot what had happened in a job.
To change these values, you need to have sysadmin access to the SQL Server Agent. Within the object explorer, right click on the SQL Server Agent node, and choose properties.
A new pop-up window will appear displaying the SQL Server Agent properties. Select the History node and the history settings are displayed:
Here you have the option to not limit the agent job history, by unchecking the corresponding box. You can also choose the maximum # of rows to store for all jobs, and an option to limit each job. The last option is to Remove history that’s older than a specified time period. This would be recommended if you do not limit the history log size, since you will not be pruning any records otherwise.