If a TimesTen database larger than 256GB is required, then you must configure Timesten in order to use large pages.
Depending upon the Operating System you are using, you should look into enabling large page support:
- either through your OS command
- or through the TimesTen daemon options file.
Number of large pages
Increasing large page settings for more memory will result in other applications (such as Oracle BI EE, Oracle Essbase) unable to allocate memory. Exceeding more than 80% of the total physical memory is not recommended.
Database shared memory calculation is:
(PermSize + TempSize + LogBufMB + 20) / hugepage_size
Example of large pages calculation for a 800GB Database:
- with a Permsize and a TempSize of 400Gb
- a Log Bufffer of 20 Mb
- and an hugepagesize of 2Mb (cat /proc/meminfo|grep Hugepagesize)
(400Gb) + (400Gb) + (1Gb) + (20Mb) = 860088172544 bit / 2 Mb = 410122 pages
With this calculation, you must the set the nr_hugepages attribute in the /etc/sysctl.conf file with the following value:
vm.nr_hugepages = 410200
and then run the following command as the root user:
On Linux, to enable large page support on TimesTen, add the following line in the TimesTen daemon options (ttendaemon.options) file:
where theis the Hugepagesize value in /proc/meminfo, specified in MB instead of KB.
cat /proc/meminfo|grep Hugepagesize
Hugepagesize: 2048 kB
We have then 2042 / 1024 = 2 Mb.
In the TimesTen daemon options (ttendaemon.options), you will add the following line:
836: Cannot create data store shared-memory segment, error 22 703: Subdaemon connect to data store failed with error TT836 The command failed. Done.
Did you reach the maximum of 256 Gb ? Then you must configure large page.