"Last delta request loaded in data target is too old: less than 1000 requests found"
One of the pre-condition is that only requests up to the oldest delta requests that were loaded to this data target can be reduced.
In order to analyse and to find out the inbound or outbound delta upload transaction RSREQREDUCE is very useful.
e.g. into infoprovider DSO_1 three different DTP are uploading data in delta update mode:
In that case one SID is very low. Call the manage screen of the infoprovider mentioned in column 'Name of Source Object for a DTP' and check if there are requests which have not been uploaded to the target since a long time. Use the button 'Request retrieved from Infoprovider'
Copy and paste the request which will be displayed when using the button, call transaction RSRQ in oder to identify the SID of the request. In the example above the highest SID 11534148 has been uploaded with SID 11,545,110.
Afterwards you can check e.g. in table RSICCONT if there are more than 1000 request available until request 11,545,110 and the timestamp which has been selected for the reduction.
"Data target xxxxx contain s less than 1000 updated requests"
In that case the TAB Ouflow: Delta Load from DTA has to be checked, if there is one DTP/Infopackage which has not been uploaded since a long time.
Two options when the root cause it a DTP which is Blocking the request reduction:
a) Start the DTP and upload the data in or out of the infoprovider
b) Delete the DTP logically with help of RSBK_LOGICAL_DELETE_DTP. After a logical deletion the DTP cannot be used anymore.
"DSO xxxxx contains less than 1000 requests without CL entry"
According to that screen there are 6159 requests which has not been deleted from the changelog. In order to reduce the requests it is mandatory that the requests have been deleted from the changelog (see SAP Note 1431315) Create process chain and make sure that the variant is correctly maintained. Have a look at KBA 1839146 which includes all known issues why changelog requests are not deleted.