Database Cache Hit Ratio (Warning)

[Rajiv Ranjan]

Hi,

Received a Database cache hit ratio warning alert from one of the
monitoring tools, the threshold for the “database cache hit ratio %” is 90%
for a High and 95% for Critical

Below hardware, CPU, disk and memory utilization of the system. Kindly
suggest the parameters for a cache hit ratio or can we simply ignore the
warning.

Hardware:
Architecture:  x86_64
CPU op-mode(s):32-bit, 64-bit
Byte Order:Little Endian
CPU(s):8
On-line CPU(s) list:   0-7
Thread(s) per core:1
Core(s) per socket:4
Socket(s): 2
NUMA node(s):  1
Vendor ID: GenuineIntel
CPU family:6
Model: 45
Model name:Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
Stepping:  2
CPU MHz:   2494.224
BogoMIPS:  4988.44
Hypervisor vendor: VMware
Virtualization type:   full
L1d cache: 32K
L1i cache: 32K
L2 cache:  256K
L3 cache:  30720K
NUMA node0 CPU(s): 0-7


Resource Utilization:

MemTotal:8008640 kB
MemFree:  145332 kB
MemAvailable:4710460 kB
Buffers:   0 kB
Cached:  6877160 kB
SwapCached:19168 kB
Active:  4853536 kB
Inactive:2575608 kB
Active(anon):2023944 kB
Inactive(anon):   694232 kB
Active(file):2829592 kB
Inactive(file):  1881376 kB
Unevictable:   0 kB
Mlocked:   0 kB
SwapTotal:   8388604 kB
SwapFree:7596796 kB
Dirty:  1660 kB
Writeback:12 kB
AnonPages:540584 kB
Mapped:  2189176 kB
Shmem:   2165612 kB
Slab: 212860 kB
SReclaimable: 151188 kB
SUnreclaim:61672 kB
KernelStack:4976 kB
PageTables:90028 kB
NFS_Unstable:  0 kB
Bounce:0 kB
WritebackTmp:  0 kB
CommitLimit:12392924 kB
Committed_AS:4439168 kB
VmallocTotal:   34359738367 kB
VmallocUsed:  169396 kB
VmallocChunk:   34359341052 kB
HardwareCorrupted: 0 kB
AnonHugePages: 77824 kB
CmaTotal:  0 kB
CmaFree:   0 kB
HugePages_Total:   0
HugePages_Free:0
HugePages_Rsvd:0
HugePages_Surp:0
Hugepagesize:   2048 kB
DirectMap4k:  174016 kB
DirectMap2M: 8214528 kB

procs ---memory-- ---swap-- -io -system--
--cpu-
 r  b   swpd   free   buff  cache   si   sobibo   in   cs us sy id
wa st
 3  0 797184 200984  0 702143600   414   24100  8  1 88
 3  0


 PID USER  PR  NIVIRTRESSHR S  %CPU %MEM TIME+ COMMAND
 3809 postgres  20   0 2439200   2.1g   2.1g S  37.2 27.2 387:11.59
postmaster
 7998 postgres  20   0 2395212 219828 217564 S  11.3  2.7   0:02.53
postmaster
 7999 postgres  20   0 2395208  58384  56200 S  11.3  0.7   0:02.07
postmaster
 8000 postgres  20   0 2395208  59456  57216 S  11.3  0.7   0:02.08
postmaster
 7214 postgres  20   0 2397520   1.9g   1.9g D  11.0 24.4   1:35.25
postmaster
 8003 postgres  20   0 2395208  57848  55656 S  10.3  0.7   0:02.08
postmaster
 8001 postgres  20   0 2399704   1.3g   1.3g D   3.3 17.1   0:15.29
postmaster
21979 postgres  20   0 2412120   2.1g   2.1g S   2.7 27.1 296:22.44
postmaster

Disk Space:
Filesystem  Size  Used Avail Use% Mounted on
/dev/mapper/localvg-rootlv  242G   68G  175G  28% /
devtmpfs3.9G 0  3.9G   0% /dev
tmpfs   3.9G  4.0K  3.9G   1% /dev/shm
tmpfs   3.9G  386M  3.5G  10% /run
tmpfs   3.9G 0  3.9G   0% /sys/fs/cgroup
/dev/sda1   497M  186M  312M  38% /boot
tmpfs   783M 0  783M   0% /run/user/1000

-- 
*Thanks,*
*Rajiv Ranjan *

Re: Database Cache Hit Ratio (Warning)

[Rajiv Ranjan]

Does this unnamed monitoring tool (and undefined query) really think higher
percentages are worse or are you mis-communicating?

Forget about the tool used for monitoring, important is to monitor the
"Cache hit ratio" is good or we can ignore it?


On Wed, 1 Apr 2020 at 10:44, David G. Johnston 
wrote:

> On Tuesday, March 31, 2020, Rajiv Ranjan  wrote:
>
>> Hi,
>>
>> Received a Database cache hit ratio warning alert from one of the
>> monitoring tools, the threshold for the “database cache hit ratio %” is
>> 90% for a High and 95% for Critical
>>
>
> Does this unnamed monitoring tool (and undefined query) really think
> higher percentages are worse or are you mis-communicating?
>
> David J.
>


-- 
*Thanks,*
*Rajiv Ranjan *