SQL and SAP error

Dear experts,

need help here, we are facing this error since few days.

this error occurs while adding a doc into SAP system. plz help

the error is as given below:

[Microsoft][SQL Server Native Client 10.0][SQL Server]Time-out occurred while waiting for buffer latch type 4 for page '' (RDR4) (1:21995), database ID 21.

this is happening in live Database.

thanks in advance.