为什么在RC隔离级别运行事务的进程如果已在另一个表上运行select语句，则会保持 IX 页锁定？我的意思是，我认为当语句结束时会释放锁（这就是为什么我们可以进行不可重复的读取）。
这是死锁xml：
<deadlock-list>
<deadlock victim="process5cd048">
<process-list>
<process id="process5cd048" taskpriority="0" logused="10000" waittime="2220" schedulerid="3" kpid="5764" status="suspended" spid="62" sbid="0" ecid="0" priority="0" trancount="1" lastbatchstarted="2012-11-09T12:16:52.730" lastbatchcompleted="2012-11-09T12:16:52.730" lastattention="2012-11-08T17:33:28.597" clientapp=".Net SqlClient Data Provider" hostname="CWCEINAW" hostpid="4908" loginname="cwcuser" isolationlevel="read committed (2)" xactid="1157173773" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="adhoc" line="1" sqlhandle="0x020000005b3f1719cc3b4ad87e96487fe7fbf624ab5c2984">
SELECT * FROM WP_CashCenter_StockTransactionLine
WHERE [StockTransaction_id] IN (
SELECT DISTINCT [ST].[id]
FROM WP_CashCenter_StockTransaction AS [ST]
LEFT JOIN WP_CashCenter_StockTransactionLine AS [STL] ON ([STL].[StockTransaction_id] = [ST].[id])
WHERE [ST].[Type] IN (1, 0, 10, 9)
AND ([STL].[Direction] IN (1, 0) OR [STL].[id] IS NULL)
AND [ST].[Status] IN (0, 1)
AND ([STL].[StockContainer_id] = 3000080311 OR [ST].[StockContainerID] = 3000080311)) </frame>
</executionStack>
<inputbuf>
SELECT * FROM WP_CashCenter_StockTransactionLine
WHERE [StockTransaction_id] IN (
SELECT DISTINCT [ST].[id]
FROM WP_CashCenter_StockTransaction AS [ST]
LEFT JOIN WP_CashCenter_StockTransactionLine AS [STL] ON ([STL].[StockTransaction_id] = [ST].[id])
WHERE [ST].[Type] IN (1, 0, 10, 9)
AND ([STL].[Direction] IN (1, 0) OR [STL].[id] IS NULL)
AND [ST].[Status] IN (0, 1)
AND ([STL].[StockContainer_id] = 3000080311 OR [ST].[StockContainerID] = 3000080311)) </inputbuf>
</process>
<process id="process33ebc8" taskpriority="0" logused="10676" waitresource="PAGE: 5:1:1144344" waittime="2221" ownerId="1157173773" transactionname="user_transaction" lasttranstarted="2012-11-09T12:16:52.197" XDES="0x41518b140" lockMode="S" schedulerid="5" kpid="5272" status="suspended" spid="62" sbid="0" ecid="9" priority="0" trancount="0" lastbatchstarted="2012-11-09T12:16:52.730" lastbatchcompleted="2012-11-09T12:16:52.730" clientapp=".Net SqlClient Data Provider" hostname="CWCEINAW" hostpid="4908" isolationlevel="read committed (2)" xactid="1157173773" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="adhoc" line="1" sqlhandle="0x020000005b3f1719cc3b4ad87e96487fe7fbf624ab5c2984">
SELECT * FROM WP_CashCenter_StockTransactionLine
WHERE [StockTransaction_id] IN (
SELECT DISTINCT [ST].[id]
FROM WP_CashCenter_StockTransaction AS [ST]
LEFT JOIN WP_CashCenter_StockTransactionLine AS [STL] ON ([STL].[StockTransaction_id] = [ST].[id])
WHERE [ST].[Type] IN (1, 0, 10, 9)
AND ([STL].[Direction] IN (1, 0) OR [STL].[id] IS NULL)
AND [ST].[Status] IN (0, 1)
AND ([STL].[StockContainer_id] = 3000080311 OR [ST].[StockContainerID] = 3000080311)) </frame>
</executionStack>
<inputbuf>
</inputbuf>
</process>
<process id="process4e13048" taskpriority="0" logused="11448" waitresource="PAGE: 5:1:1144209" waittime="2172" ownerId="1157175935" transactionname="user_transaction" lasttranstarted="2012-11-09T12:16:52.997" XDES="0x3458e63b0" lockMode="S" schedulerid="7" kpid="3912" status="suspended" spid="58" sbid="0" ecid="0" priority="0" trancount="1" lastbatchstarted="2012-11-09T12:16:53.070" lastbatchcompleted="2012-11-09T12:16:53.067" clientapp=".Net SqlClient Data Provider" hostname="CWCEINAW" hostpid="4908" loginname="cwcuser" isolationlevel="read committed (2)" xactid="1157175935" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="adhoc" line="1" stmtstart="160" sqlhandle="0x02000000193c8a3bb37a516f7a7155b01a67b7772459f53e">
SELECT [D].*
FROM WP_Discrepancy as [D]
WHERE [D].[Level] = @Level
AND [D].[Status] IN (@StatusInProgress, @StatusConfirmed)
AND [D].[StockContainerID] = @StockContainerID </frame>
<frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000">
unknown </frame>
</executionStack>
<inputbuf>
(@Level int,@StatusInProgress int,@StatusConfirmed int,@StockContainerID bigint)SELECT [D].*
FROM WP_Discrepancy as [D]
WHERE [D].[Level] = @Level
AND [D].[Status] IN (@StatusInProgress, @StatusConfirmed)
AND [D].[StockContainerID] = @StockContainerID </inputbuf>
</process>
</process-list>
<resource-list>
<exchangeEvent id="Pipe43a6da400" WaitType="e_waitPipeGetRow" nodeId="1">
<owner-list>
<owner id="process33ebc8"/>
</owner-list>
<waiter-list>
<waiter id="process5cd048"/>
</waiter-list>
</exchangeEvent>
<pagelock fileid="1" pageid="1144344" dbid="5" objectname="WebPortal.dbo.WP_CashCenter_StockTransactionLine" id="lock326ee4180" mode="IX" associatedObjectId="72057594149601280">
<owner-list>
<owner id="process4e13048" mode="IX"/>
</owner-list>
<waiter-list>
<waiter id="process33ebc8" mode="S" requestType="wait"/>
</waiter-list>
</pagelock>
<pagelock fileid="1" pageid="1144209" dbid="5" objectname="WebPortal.dbo.WP_Discrepancy" id="lock339da6b80" mode="SIX" associatedObjectId="72057594163625984">
<owner-list>
<owner id="process5cd048" mode="SIX"/>
</owner-list>
<waiter-list>
<waiter id="process4e13048" mode="S" requestType="wait"/>
</waiter-list>
</pagelock>
</resource-list>
</deadlock>
</deadlock-list>
正如您所见，流程 process4e13048 在表WP_CashCenter_StockTransactionLine的某些页面上拥有 IX 锁。尝试执行的当前语句是SELECT，无法完成，因为它需要WP_Discrepancy页面上的共享锁定（很明显）与进程持有的 SIX 锁定冲突的 process5cd048 即可。
同样，为什么后一个过程会持有 SIX 锁？根据执行堆栈，正在执行的语句是SELECT到WP_CashCenter_StockTransactionLine表。
如果我使用 Serializable IL运行事务，我希望同一进程中先前语句获取的锁保留。但事实并非如此。
任何人都能解释一下我对RC隔离级别的错误吗？ 感谢。
答案 0 :(得分：1)
我认为当语句结束时会释放锁
不写锁（X，IX，S-IX等）。写锁必须遵守two phase locking，因此它们在事务结束时被释放。想想相反的意思：DELETE在事务结束前删除行上的X锁定，稍后并发事务用相同的键INSERT一个新行（它可以，因为没有锁定），现在第一个事务需要回滚。它能做什么，它无法插回它删除的行，因为密钥是在第二个事务的同时获取的，所以它无法回滚。
因此运行SELECT时会发生死锁，因为运行这些选择的事务在运行SELECT之前已获取写锁。