You use the Date Compr. Registers window to view all the date compressions that have been done. With date compression, you combine several old entries in one new one. The window contains a line for each compression. The line contains many details about the date compression and the entries it comprises.
There are a number of batch jobs that create entries in the date compression registers, for example: Date Compress General Ledger, Date Compress Customer Ledger, Delete Check Ledger Entries, and Date Compress Insurance Ledger.