Re: randomize_va_space

On 5/9/23 18:37, Alan Sterger wrote:
> Hello Listers,
>
> On a multi Oracle homed (12c and 19c) RHEL 7.9 server, have started to
> observe infrequent (every 2 months) 'ORA-00445: background process
> "m001" did not start after 120 seconds' errors from both 12c and 19c
> instances.  Seeing the same error from two different Oracle releases
> sort of points to a server kernel issue, specifically
> kernel.randomize_va_space=2.
>
> MOS Note 1345364.1 implies randomize_va_space was a thing in the past
> (11g,12c).  However, appears Oracle is still recommending disabling in
> 19c on Oracle Cloud Infrastructure.
>
> What is your on-prem randomize_va_space?
>
> Thanks,
>
> -- Alan Sterger
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
I always set it to 0 on my remaining RHEL 7 installations, regardless of the database version. Address space randomization doesn't look like a useful feature from my perspective. Here is the Linux documentation for the parameter:

    randomize_va_space
    <https://www.kernel.org/doc/html/latest/admin-guide/sysctl/kernel.html#id73><https://www.kernel.org/doc/html/latest/admin-guide/sysctl/kernel.html#randomize-va-space>

This option can be used to select the type of process address space randomization that is used in the system, for architectures that support this feature.

0         

Turn the process address space randomization off. This is the default for architectures that do not support this feature anyways, and kernels that are booted with the "norandmaps" parameter.

1         

Make the addresses of mmap base, stack and VDSO page randomized. This, among other things, implies that shared libraries will be loaded to random addresses. Also for PIE-linked binaries, the location of code start is randomized. This is the default if the |CONFIG_COMPAT_BRK| option is enabled.

2         

Additionally enable heap randomization. This is the default if |CONFIG_COMPAT_BRK| is disabled.

There are a few legacy applications out there (such as some ancient versions of libc.so.5 from 1996) that assume that brk area starts just after the end of the code+bss. These applications break when start of the brk area is randomized. There are however no known non-legacy applications that would be broken this way, so for most systems it is safe to choose full randomization.

Systems with ancient and/or broken binaries should be configured with |CONFIG_COMPAT_BRK| enabled, which excludes the heap from process address space randomization.

However, the parameter no longer exists in Oracle Linux 8:

    [oracle_at_ora23c ~]$ sudo sysctl -p|grep -i random     [oracle_at_ora23c ~]$ cat /etc/oracle-release     Oracle Linux Server release 8.7
    [oracle_at_ora23c ~]$

And yes, the VM houses Oracle 23c.

[oracle_at_ora23c dbhomeFree]$ sqlplus scott/tiger_at_localhost/freepdb1.home.com

SQL*Plus: Release 23.0.0.0.0 - Developer-Release on Wed May 10 14:55:05 2023 Version 23.2.0.0.0

Copyright (c) 1982, 2023, Oracle.  All rights reserved.

Last Successful login time: Sat Apr 15 2023 21:49:22 -04:00

Connected to:
Oracle Database 23c Free, Release 23.0.0.0.0 - Developer-Release Version 23.2.0.0.0

SQL>

-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com

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