SSRS 2008 R2 错误：Timeout expired. The timeout period

今天遇到了Reporting Services（SQL SERVER 2008 R2）的报表执行异常情况，报表加载数据很长时间都没有响应，最后报“An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database.;”。检查C:/PRogram Files/Microsoft SQL Server/MSRS10_50.MSSQLSERVER/Reporting Services/LogFiles下日志，发现ReportServerService__12_24_2014_10_29_02.log中有大量如下错误：

library!WindowsService_4!1308!12/24/2014-01:27:53:: ;i INFO: Call to CleanBatch() 

library!WindowsService_4!1308!12/24/2014-01:32:53:: ;e ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException: , An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database.; 

dbcleanup!WindowsService_4!1308!12/24/2014-01:32:53:: ;e ERROR: Sql Error in CleanOrphanedSnapshots: Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException: An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database. ---> System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the Operation or the server is not responding. 

library!WindowsService_4!1308!12/24/2014-01:32:53:: ;i INFO: Cleaned 0 batch records, 0 policies, 0 sessions, 0 cache entries, 0 snapshots, 0 chunks, 0 running jobs, 0 persisted streams, 0 segments, 0 segment mappings, 0 edit sessions. 

library!WindowsService_4!1308!12/24/2014-01:32:53:: ;i INFO: Call to CleanBatch() ends 

library!WindowsService_4!13ec!12/24/2014-01:37:53:: ;i INFO: Call to CleanBatch() 

library!WindowsService_4!13ec!12/24/2014-01:42:53:: ;e ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException: , An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database.;