执行yum出错：db4 error(22) from db->close

   今天在内网测试机上yum安装nfs时突然遇到一个错误，yum出错信息如下：

[root@base2 bin]# yum -y install nfs-utils portmap
rpmdb: Lock table is out of available locker entries
rpmdb: Unknown locker ID: eef
error: db4 error(22) from db->close: Invalid argument
error: cannot open Packages index using db3 - Cannot allocate memory (12)
error: cannot open Packages database in /var/lib/rpm
Traceback (most recent call last):
  File "/usr/bin/yum", line 29, in ?
    yummain.main(sys.argv[1:])
  File "/usr/share/yum-cli/yummain.py", line 85, in main
    base.getOptionsConfig(args)
  File "/usr/share/yum-cli/cli.py", line 163, in getOptionsConfig
    disabled_plugins=self.optparser._splitArg(opts.disableplugins))
  File "/usr/lib/python2.4/site-packages/yum/__init__.py", line 164, in _getConf
    self._conf = config.readMainConfig(startupconf)
  File "/usr/lib/python2.4/site-packages/yum/config.py", line 685, in readMainCo
    yumvars['releasever'] = _getsysver(startupconf.installroot, startupconf.dist
  File "/usr/lib/python2.4/site-packages/yum/config.py", line 752, in _getsysver
    idx = ts.dbMatch('provides', distroverpkg)
TypeError: rpmdb open failed

这个还是第一次碰到，查看错误意思是DB错误，上网查找后也是时候rpm的db数据库的问题，所以解决办法如下：
 

rm -f /var/lib/rpm/__db.00*    #删除旧有数据库
rpm --rebuilddb                   #重建新数据库

重建完毕后，重新执行安装：yum -y install nfs-utils portmap
  测试可以正常安装，问题解决。