SQL2043N 与 linux的randomize_va_space特性

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[db2inst1@limt ~]$ db2 ? SQL2043N

SQL2043N  Unable to start a child process or thread.
Explanation: 
Unable to start up the child processes or threads required during the
processing of a database utility. There may not be enough available
memory to create the new process or thread. The utility stops
processing.
User response: 
Ensure the system limit for number of processes or threads has not been
reached (either increase the limit or reduce the number of processes or
threads already running). Ensure that there is sufficient memory for the
new process or thread. Resubmit the utility command  

Problem(Abstract)
ASLR or Address Space Layout Randomization is a feature that is activated by default on some of the newer linux distributions. It is designed to load shared memory objects in random addresses.

In DB2, multiple processes map a shared memory object at the same address across the processes. It was found that DB2 cannot guarantee the availability of address for the shared memory object when ASLR is turned on.

Important note: DB2 10.1 has been enhanced so that ASLR can be safely enabled.
Symptom
This conflict in the address space means that a process trying to attach a shared memory object to a specific address may not be able to do so, resulting in a failure in shmat subroutine. However, on subsequent retry (using a new process) the shared memory attachment may work. The result is a random set of failures. Some processes that have been known to see this error are: db2pd, db2egcf, and db2vend.
Some of the behaviors seen include the following:
For the db2pd command, it will report no data found even through the instance / database is active:
Database SAMPLE not activated on database partition 0.

For the db2egcf process, used for HA monitoring, the db2egcf may incorrectly determine the instance is down and initiate a failover.

For the db2vend process, backup and log archive methods might fail with an error indicating a child process could not be started:
SQL2043N  Unable to start a child process or thread.  


Diagnosing the problem
When this problem is suspected, check db2diag.log for the shmat failure like the following. Note that the same error message can also occur for a different cause. Hence, it's important to note the process that reported this error.

FUNCTION: DB2 UDB, SQO Memory Management, sqlocshr, probe:180
MESSAGE : ZRC=0x850F0005=-2062614523=SQLO_NOSEG
          "No Storage Available for allocation"
          DIA8305C Memory allocation failure occurred.
CALLED  : OS, -, shmat                    OSERR: EINVAL (22)
Resolving the problem
1) Disable ASLR temporarily (change is only effective until next boot):
Run "sysctl -w kernel.randomize_va_space=0" as root.

2) Disable ASLR immediately and on all subsequent reboots:

Add the following line to /etc/sysctl.conf:
kernel.randomize_va_space=0
and then run "sysctl -p" as root to make the change take effect immediately.  

为2则表示在1的基础上进一步打开堆地址随机化。在打开堆地址随机化之前，堆的起始位置是紧接着应用程序bss段之后的。       

的监控数据，所以db2pd为轻量级工具，对数据库的性能影响比较少

SQL2043N 与 linux的randomize_va_space特性

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原文地址：http://blog.csdn.net/lmt818583/article/details/41986219