If this is 11.2.0.4, you should consider setting _realfree parameters to
true and set _realfree_heap_pagesize_hint to 256k or so. Default is 64k and
you may not need to adjust the kernel parameter. For 12c, i think, the
parameter names were a bit different.
On Tue, Nov 10, 2020, 7:47 AM Johannes Vibe Djernæs <jodje@xxxxxxxxxxxx>
wrote:
Hi Mark
Thanks, I already had a look at that page, but I didn't find anything to
help calculate an appropriate value for an Oracle database
- I guess the problem is to find out how manny mmap()'ed areas are needed
...
I did find some notes on Oracle support (or was it just somewhere else on
the net) where someone had run into memory errors, that were fixed by
increasing the value of vm.max_map_count, but nothing about why a
particular value was chosen ...
- it all seemed very random ...
Johannes
--
Johannes Vibe Djernæs
Mobil: +45 53 747 102
Miracle 42 A/S
Consulting & Managed Services
https://miracle42.dk
Den 10. nov. 2020 kl. 16.32 skrev Mark J. Bobak <mark@xxxxxxxxx>:
Hmm...I've never heard of this before, but it's apparently the number of
mmap()'ed areas you can have.
Documented here:
https://www.kernel.org/doc/Documentation/sysctl/vm.txt
(Search for 'max_map_count')
Hope that helps,
-Mark
PS The default is 65536, and since I've been running Oracle on Linux for
a while now, and I've never run into this parameter before, I'm guessing
there's (almost?) no way an Oracle database will ever hit this limit...?
On Tue, Nov 10, 2020 at 5:26 AM Johannes Vibe Djernæs <jodje@xxxxxxxxxxxx>
wrote:
Hi
I am configuring a couple of Oracle Linux Server release 6.8 and 6.10
servers with each 500G memory for an Oracle 11.2 db and is of cause
configuring them with appropriate HugePages.
However, I have come across the kernel parameter vm.max_map_count, but I
have not been able to find any solid description about how to determine an
appropriate value for this parameter and what should be considered
- do any of you have recommendations on that issue?
- maybe just a link to a propper description?
Cheers
Johannes
--
Johannes Vibe Djernæs
Mobil: +45 53 747 102
Miracle 42 A/S
Consulting & Managed Services
https://miracle42.dk
