Sometime you as DBA you need to check your memory On Operating System Level, i will give you some command will useful to you :
1-free -m / free -g
m : megabytes
g : gigabytes
total used free shared buffers cached
Mem: 503 451 52 0 14 293
-/+ buffers/cache: 143 360
Swap: 1027 0 1027
another example :
free -t -m
total used free shared buffers cached
Mem: 750 625 125 0 35 335
-/+ buffers/cache: 253 496
Swap: 956 0 956
Total: 1707 625 1082
2-vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 0 131620 35432 341496 0 0 42 82 737 1364 15 3 81 1
3-top
4-gnome-system-monitor
The below Command for clear cache memory in linux
sync;
echo 3 > /proc/sys/vm/drop_caches
you can make it as job in linux save in it crontab
0 * * * * /root/clearcache.sh
Create a file in '/root' called 'clearcache.sh' with the following content:
#!/bin/sh
sync; echo 3 > /proc/sys/vm/drop_caches
Thank you
osama mustafa