[20170704]JOXSHM_EXT_x files on Linux.txt
--//昨天看链接www.itpub.net/thread-2089507-1-1.html时,发现我的一台测试机器有1堆文件在目录/dev/shm下:
$ ls -l /dev/shm | head
total 724
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:44 JOXSHM_EXT_0_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_10_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_11_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_12_test_30113794
-rwxrwx--- 1 oracle11g oinstall 12288 2015-07-08 08:38:45 JOXSHM_EXT_13_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_14_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_15_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_16_test_30113794
-rwxrwx--- 1 oracle11g oinstall 4096 2015-07-08 08:38:45 JOXSHM_EXT_17_test_30113794
--//还可以发现这些打头的文件:
-rwx------ 1 oracle oinstall 3824 2016-09-02 09:45:42 PESLD_book_4e98004_10218b6900000000
-rwx------ 1 oracle oinstall 40200 2016-09-02 09:45:46 PESLD_book_4e98004_406e246900000000
-rwx------ 1 oracle oinstall 1104 2016-09-02 09:45:48 PESLD_book_4e98004_704f9b7d00000000
-rwx------ 1 oracle oinstall 608 2016-09-02 09:46:17 PESLD_book_4e98004_9001327d00000000
-rwx------ 1 oracle oinstall 2096 2016-09-02 09:45:46 PESLD_book_4e98004_b867926900000000
-rwx------ 1 oracle oinstall 1832 2016-09-02 09:45:48 PESLD_book_4e98004_c06b9f7d00000000
-rwx------ 1 oracle oinstall 720 2017-05-09 11:17:51 PESLD_book_a250003_b8749a7b00000000
$ du -sk /dev/shm
724 /dev/shm
--//占用空间不大仅仅724K.
--//google,发现如下连接://blog.tanelpoder.com/2014/05/09/what-the-heck-are-the-devshmjoxshm_ext_x-files-on-linux/.
--//按照文章的介绍,test应该对应是sid,而我这个实例早不存在.而里面存在一堆文件.我仅仅估计异常关闭数据库时没有清理.
--//我通过测试说明情况:
SYS@book> @ &r/ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
SCOTT@book> SHOW PARAMETER jit
NAME TYPE VALUE
----------------- -------- ------
java_jit_enabled boolean TRUE
$ ls -l /dev/shm | wc
573 4578 49135
--//当前573个!!
SCOTT@book> @ &r/spid
SID SERIAL# SPID PID P_SERIAL# C50
---------- ---------- ------ ------- ---------- --------------------------------------------------
56 11 57854 29 4 alter system kill session '56,11' immediate;
SCOTT@book> SELECT DBMS_JAVA.GETVERSION FROM dual;
GETVERSION
-----------
11.2.0.4.0
$ ls -l /dev/shm | wc
737 5890 63129
--//你可以发现执行后文件数量增加了.737-573=164
$ ls -l /dev/shm | grep 2017-07-04 | wc
164 1312 13994
--//注我喜欢讲ls定义别名如下
$ alias ls
alias ls='ls --color=auto --time-style=+"%Y-%m-%d %H:%M:%S"'
--//这样当天的日期能正常显示.比较符合国人的显示时间风格.
--//正好增加164个.
$ ls -l /dev/shm | grep 2017-07-04 | head
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:39 JOXSHM_EXT_0_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:39 JOXSHM_EXT_100_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:39 JOXSHM_EXT_101_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:39 JOXSHM_EXT_102_book_188153859
-rwxrwx--- 1 oracle oinstall 8192 2017-07-04 08:57:39 JOXSHM_EXT_103_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:40 JOXSHM_EXT_104_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:40 JOXSHM_EXT_105_book_188153859
-rwxrwx--- 1 oracle oinstall 8192 2017-07-04 08:57:40 JOXSHM_EXT_106_book_188153859
-rwxrwx--- 1 oracle oinstall 4096 2017-07-04 08:57:40 JOXSHM_EXT_107_book_188153859
-rwxrwx--- 1 oracle oinstall 53248 2017-07-04 08:57:40 JOXSHM_EXT_108_book_188153859
--//正常退出会话后.
$ ls -l /dev/shm | grep 2017-07-04 | wc
164 1312 13994
--//可以发现依旧存在!!
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
$ ls -l /dev/shm | grep 2017-07-04 | wc
0 0 0
--//你可以发现正常关闭这些文件会消失,或者这些内存的东西会回收.这样可以断定留下那些是异常关闭数据库留下的.
--//可以重复测试来证明自己的观点.
SYS@book> startup
ORACLE instance started.
Total System Global Area 634732544 bytes
Fixed Size 2255792 bytes
Variable Size 197133392 bytes
Database Buffers 427819008 bytes
Redo Buffers 7524352 bytes
Database mounted.
Database opened.
$ ls -l /dev/shm | grep 2017-07-04 |wc
0 0 0
SYS@book> SELECT DBMS_JAVA.GETVERSION FROM dual;
GETVERSION
-----------
11.2.0.4.0
$ ls -l /dev/shm | grep 2017-07-04 | wc
145 1160 12360
SYS@book> shutdown abort
ORACLE instance shut down.
$ ls -l /dev/shm | grep 2017-07-04 | wc
145 1160 12360
--//你可以发现异常关闭这些就留在/dev/shm中,消耗内存.估计进程异常kill,应该也是一样的.当然这些消耗的内存并不多,我查看几台
--//发现最大消耗9M.
--//我建议在启动数据库前实际上可以删除这些垃圾的.我全部清除后启动数据库一点问题都没有.当然要注意一些应用也可能使用这部分
--//内存,在删除前要仔细查看.
--//转抄官方的介绍:
http://docs.oracle.com/cd/E17116_01/doc/readmes.112/e11015/toc.htm#BABBCFHJ
30.1 Secure Database By Default Changes
The PUBLIC EXECUTE privilege for the DBMS_RANDOM PL/SQL package will be deprecated in future Oracle Database releases
(reference Bug 7591837). Users who need to run this PL/SQL package should be given explicit EXECUTE privileges.
30.2 Stale Native Code Files Are Being Cached
Natively compiled PL/SQL and native code generated by the JIT compiler for Oracle JVM, may be cached in operating system
files. The SHUTDOWN ABORT and SHUTDOWN IMMEDIATE commands do not clean these cached native code files (reference Bug
8527383).
To avoid problems caused by stale files in the cache, clean the files before restarting the database instance. The stale
files that belong to the instance can be identified by name. The name patterns are as follows where sid_name is the
system identifier name:
JOXSHM_EXT_*_sid_name_*
PESHM_EXT_*_sid_name_*
PESLD_sid_name_*
It is advisable to remove stale files as part of a startup script. For example, to clean stale files for the instance
passed to the startup csh script by name on Linux, add the following three lines to the startup script:
rm JOXSHM_EXT_*_$1_*
rm PESHM_EXT_*_$1_*
rm PESLD_$1_*
The location of the native cache depends on the platform. It is defined by the location of files created by the
operating system to implement shm_open requests on that platform. For example, Solaris stores shared memory segments in
/var/tmp/.SHMD and /tmp/.SHMD. Linux stores them in /dev/shm.
