在oracle.jdbc.driver.T4CConnection上找到的锁定对象

Question

我正在使用JMC执行应用程序分析,我没有看到任何锁定/线程争用,如下面的屏幕截图所示.

我在下面运行SQL(每隔几秒)也没有返回任何结果.

select 
   (select username from v$session where sid=a.sid) blocker,
   a.sid,
   ' is blocking ',
   (select username from v$session where sid=b.sid) blockee,
   b.sid
from 
   v$lock a, 
   v$lock b
where 
   a.block = 1
and 
   b.request > 0
and 
   a.id1 = b.id1
and 
   a.id2 = b.id2;

什么可能是锁数据库连接的原因？它可能是数据库记录/表锁吗？

下面是我在程序执行期间提取的线程转储,它似乎永远在运行.

   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:170)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at oracle.net.ns.Packet.receive(Packet.java:283)
    at oracle.net.ns.DataPacket.receive(DataPacket.java:103)
    at oracle.net.ns.NetInputStream.getNextPacket(NetInputStream.java:230)
    at oracle.net.ns.NetInputStream.read(NetInputStream.java:175)
    at oracle.net.ns.NetInputStream.read(NetInputStream.java:100)
    at oracle.net.ns.NetInputStream.read(NetInputStream.java:85)
    at oracle.jdbc.driver.T4CSocketInputStreamWrapper.readNextPacket(T4CSocketInputStreamWrapper.java:123)
    at oracle.jdbc.driver.T4CSocketInputStreamWrapper.read(T4CSocketInputStreamWrapper.java:79)
    at oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1122)
    at oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1099)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:288)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:191)
    at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:523)
    at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:207)
    at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:863)
    at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1153)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1275)
    at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3576)
    at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3620)
    - locked <0x00000007af3423c0> (a oracle.jdbc.driver.T4CConnection)

Answer 1

您在此处将数据库锁与Java锁混淆.JMC只显示Java程序中的锁(同步块,等待等),它对数据库内部的内容一无所知.您的SQL查询仅显示数据库级别的锁(表锁,行锁等),并且对Java程序中的锁一无所知.这些是绝对不同的领域和绝对不同的锁.

你在这里有一个线程的转储,该线程T4CConnection使用地址对类型的对象进行锁定0x7af3423c0.它只表示此线程正在执行某个synchronized(connection)块内的代码.就这样.线程没有被其他线程阻塞(否则它的状态不会RUNNABLE,它会是WAITING或BLOCKED).它正在运行并从网络套接字读取内容(可能是来自数据库的响应).

这种行为绝对正常.DB驱动程序在执行SQL查询的过程中对连接实例执行同步,以允许其他线程并行使用它.

在此屏幕截图和此线程转储中,您无需担心任何问题.