今天遇到了Reporting Services（SQL SERVER 2008 R2）的報表執行異常情況，報表加載數據很長時間都沒有響應，最后報“An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database.;”。檢查C:\Program Files\Microsoft SQL Server\MSRS10_50.MSSQLSERVER\Reporting Services\LogFiles下日志，發現ReportServerService__12_24_2014_10_29_02.log中有大量如下錯誤：
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.;
dbcleanup!WindowsService_4!13ec!12/24/2014-01:42:53:: ;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!13ec!12/24/2014-01:42:53:: ;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!13ec!12/24/2014-01:42:53:: ;i INFO: Call to CleanBatch() ends
library!WindowsService_4!1308!12/24/2014-01:47:53:: ;i INFO: Call to CleanBatch()
library!WindowsService_4!1308!12/24/2014-01:52:53:: ;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!12/24/2014-01:52:53:: ;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!12/24/2014-01:52:53:: ;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!12/24/2014-01:52:53:: ;i INFO: Call to CleanBatch() ends
檢查了服務器的存儲情況后，可以排除low disk問題，只能是connection failure, timeout的問題，於是我查看1點多的執行記錄，發現取數據時間都是幾百秒，如下截圖所示
我檢查C:\Program Files\Microsoft SQL Server\MSRS10_50.MSSQLSERVER\Reporting Services\ReportServer下的rsreportserver.config,發現DatabaseQueryTimeout為120秒
但是這些報表的SQL語句我在SSMS里面執行過，也只有1~2秒，根本不會超時的情況。當時我立馬重啟了SSRS服務后，問題解決。那么問題究竟出自哪里呢？搜索了網上很多資料，大致有下面一些原因：
原因1：SSRS服務崩潰了，不能響應用戶請求。
These threads could help: SSRS 2008 crashing when running a report with huge amount of data long running report can not be rendered in Report Manager .....
- SSRS 2008 crashing when running a report with huge amount of data
- long running report can not be rendered in Report Manager or through Subscription
具體可以參見“參考資料”選URL中的討論。
原因2：Database deadlocks occur when you try to view an SSRS report in the SharePoint integrated mode after you update a data source
具體可以參考官方文檔http://support.microsoft.com/kb/2691331/en-us ，不過由於我們服務器並沒有應用SharePoint integrated mode，所以應該可以排除。
原因3：Cannot rename a report in SharePoint integrated mode.這個核查過后，也可以排除。
至此，由於第一次遇到這個錯誤，搜索了大量資料也沒有看到一個很明確的答案，加之SSRS確實也是問題多多。所以我覺得應該是SSRS服務崩潰了。如有不對，敬請指出。
參考資料：
http://support.microsoft.com/kb/2691331/en-us
http://blog.davyknuysen.be/2010/09/22/cannot-rename-a-report-in-sharepoint-integrated-mode/