The maximum number of Call Details Records (CDRs) that can be stored on a Cisco CallManager server really depends on the size of the hard drive on the server. Technically, 2.1 billion CDR records is the maximum number that can be stored, and the default is 1.5 million records.
The Max CDR Records service parameter controls the maximum number of CDRs on the system. When this limit is exceeded, the oldest CDRs are automatically removed, along with the related Call Management Records (CMRs), once a day.
CDR Analysis and Reporting (CAR) reports can be viewed in a PDF or CSV format. PDFs are limited to 5,000 records, while CSVs are limited to 20,000 records.
In order to get around these limits, reduce the date range and generate the reports. If a PDF format is used, try a CSV format instead.