Thread: Database Cache Hit Ratio (Warning)
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_64CPU 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 so bi bo in cs us sy id wa st
3 0 797184 200984 0 7021436 0 0 414 241 0 0 8 1 88 3 0
PID USER PR NI VIRT RES SHR 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% /
devtmpfs 3.9G 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
On Tuesday, March 31, 2020, Rajiv Ranjan <rajiv.mca08@gmail.com> 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.
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 <david.g.johnston@gmail.com> wrote:
On Tuesday, March 31, 2020, Rajiv Ranjan <rajiv.mca08@gmail.com> 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 CriticalDoes this unnamed monitoring tool (and undefined query) really think higher percentages are worse or are you mis-communicating?David J.
Thanks,
Rajiv Ranjan
On Fri, Apr 3, 2020 at 5:17 AM Rajiv Ranjan <rajiv.mca08@gmail.com> wrote:
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?
The query at least would help, since it seems to be measuring something other that "cache hit ratio".
I'm not in a position to judge whether monitoring "cache hit ratio" is something you should be doing in your situation. It provides information and is fairly cheap to capture and store. From the sounds of it you should probably continue capturing the data but turn off the alert. That way if there is a problem the data still exists to be considered. The metric itself does not measure something of critical importance.
David J.