內存耗盡導致系統緩慢的解決方法
一套測試庫系統響應緩慢，通SQLPLUS登陸到數據庫中大約5-6秒才能登陸進去，正常情況下也就1秒即可登陸，簡單的一個show parameter 命令也得好幾秒才返回。下面YJBYS小編為大家整理了關于內存耗盡導致系統緩慢的解決方法，希望對你有所幫助。
登陸到數據庫中發現ALERT文件報了大量的ORA-3136錯誤信息。
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
Tue Jan 10 11:19:17 2012
WARNING: inbound connection timed out (ORA-3136)
ORA-3136錯誤一般在網絡不穩定，數據庫系統資源耗盡的時候，客戶端進行連接的時候容易出現。
topas一下發現系統的內存資源耗光了，交換空間都用掉了30%多。
MEMORY
Real,MB 32768
% Comp 39.6
% Noncomp 61.2
% Client 61.2
PAGING SPACE
Size,MB 32768
% Used 31.1
% Free 68.8
大部分內存都被客戶端分頁占掉了。
數據庫的物理內存為32G，交換空間為32G如下：
$ lsattr -El mem0
goodsize 32768 Amount of usable physical memory in Mbytes False
size 32768 Total amount of physical memory in Mbytes False
$ lsps -a
Page Space Physical Volume Volume Group Size %Used Active Auto Type
paging00 hdisk1 rootvg 16384MB 31 yes yes lv
hd6 hdisk0 rootvg 16384MB 31 yes yes lv
$
檢查了一下數據庫配置ORACLE的SGA,PGA都設置的不大
SQL> show parameter sga
NAME TYPE VALUE
------------------------------------ ---------------------- -----------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 10G
sga_target big integer 10G
SQL> show parameter pga
NAME TYPE VALUE
------------------------------------ ---------------------- -----------
pga_aggregate_target big integer 4G
總共才14G，還有大約18G的空間可供操作系統利用，不應該出現內存緊張的問題。
$ vmstat -v
8388608 memory pages
7961825 lruable pages
10110 free pages
4 memory pools
994480 pinned pages
80.0 maxpin percentage
20.0 minperm percentage
80.0 maxperm percentage
63.9 numperm percentage
5093543 file pages
0.0 compressed percentage
0 compressed pages
63.9 numclient percentage
80.0 maxclient percentage
5093543 client pages
0 remote pageouts scheduled
32561 pending disk I/Os blocked with no pbuf
18706130 paging space I/Os blocked with no psbuf
2740 filesystem I/Os blocked with no fsbuf
200 client filesystem I/Os blocked with no fsbuf
1904898 external pager filesystem I/Os blocked with no fsbuf
0 Virtualized Partition Memory Page Faults
0.00 Time resolving virtualized partition memory page faults
通過vmstat -v 發現系統的內核參數 maxperm, maxclient 都設置為80%，對于數據庫系統來說，這個設置的太高了。
numperm percentage 都達到了63.9 了，大部分內存都被文件系統緩存占掉了。
切換到root用戶執行如下命令：
SXTESTDB11@/# vmo -p -o maxclient%=30 -o maxperm%=30 -o minperm%=10 -o strict_maxclient=1
Setting minperm% to 10 in nextboot file
Setting maxperm% to 30 in nextboot file
Setting maxclient% to 30 in nextboot file
Setting strict_maxclient to 1 in nextboot file
Setting minperm% to 10
Setting maxperm% to 30
Setting maxclient% to 30
Setting strict_maxclient to 1
SXTESTDB11@/# vmo -L | grep strict
strict_maxclient 1 1 1 0 1 boolean D
strict_maxperm
strict_maxperm 0 0 0 0 1 boolean D
strict_maxclient
一段時間后系統內存恢復正常;
$ vmstat -v
8388608 memory pages
7961825 lruable pages
2700191 free pages
4 memory pools
994864 pinned pages
80.0 maxpin percentage
10.0 minperm percentage
30.0 maxperm percentage
29.9 numperm percentage
2384473 file pages
0.0 compressed percentage
0 compressed pages
29.9 numclient percentage
30.0 maxclient percentage
2384473 client pages
0 remote pageouts scheduled
32561 pending disk I/Os blocked with no pbuf
18706130 paging space I/Os blocked with no psbuf
2740 filesystem I/Os blocked with no fsbuf
200 client filesystem I/Os blocked with no fsbuf
1904898 external pager filesystem I/Os blocked with no fsbuf
0 Virtualized Partition Memory Page Faults
0.00 Time resolving virtualized partition memory page faults
numperm percentage 已經大大降低。
topas系統內存情況如下：
MEMORY
Real,MB 32768
% Comp 39.6
% Noncomp 28.9
% Client 28.9
再次登錄數據庫，即可瞬間完成。
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