Oralce swap 100%案例分析

操作系统版本：CentOS 5.8 64bit

数据库版本：11.2.0.1

问题描述：

最近对数据库添加内存到32G，并调大了MEMORY_MAX_SIZE参数为28G，MEMORY_TARGET参数为24G；运行了一小段时间，没有发现大的问题，只是nagios监控到主库和备库的swap使用率偏高，而在添加内存之前并未出现过这种情况，调整前操作系统内存大小为16G，调整后MEMORY_MAX_SIZE和MEMORY_TARGET参数均为11G！

调整前交换分区使用率：

1:主库的交换分区使用率平均值为7.11%
[root@db1 ~]# sar -f /var/log/sa/sa11 -r
11:41:01 PM kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad
11:42:01 PM 93760 16332056 99.43 124792 13621548 7610880 582260 7.11 280
11:43:01 PM 87104 16338712 99.47 125084 13622556 7610880 582260 7.11 280
11:44:01 PM 79484 16346332 99.52 125384 13624140 7610880 582260 7.11 280
11:45:01 PM 77632 16348184 99.53 125684 13625580 7610880 582260 7.11 280
11:46:01 PM 62852 16362964 99.62 125936 13634280 7610880 582260 7.11 280
11:47:01 PM 58452 16367364 99.64 126484 13635080 7610880 582260 7.11 280
11:48:01 PM 61328 16364488 99.63 126856 13639772 7610880 582260 7.11 280
11:49:01 PM 64116 16361700 99.61 127040 13630580 7610880 582260 7.11 280
11:50:01 PM 65820 16359996 99.60 127268 13625496 7610880 582260 7.11 280
11:51:01 PM 59888 16365928 99.64 127148 13588072 7610880 582260 7.11 280
11:52:01 PM 84152 16341664 99.49 127412 13589552 7610880 582260 7.11 280
11:53:01 PM 102492 16323324 99.38 127716 13590332 7610880 582260 7.11 280
11:54:01 PM 96444 16329372 99.41 128076 13602516 7610880 582260 7.11 280
11:55:01 PM 88752 16337064 99.46 128408 13607108 7610880 582260 7.11 280
11:56:01 PM 78936 16346880 99.52 128708 13608816 7610880 582260 7.11 280
11:57:01 PM 57192 16368624 99.65 128936 13609668 7610880 582260 7.11 280
11:58:01 PM 64308 16361508 99.61 129192 13611012 7610880 582260 7.11 280
11:59:01 PM 62620 16363196 99.62 129476 13612704 7610880 582260 7.11 280
Average: 94185 16331631 99.43 125388 13559392 7610581 582559 7.11 289

2：备库的交换分区使用率平均值为12.27%
11:41:01 PM kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad
11:42:01 PM 97084 16328732 99.41 283368 14770184 7187548 1005592 12.27 23924
11:43:01 PM 95968 16329848 99.42 283396 14770264 7187548 1005592 12.27 23924
11:44:01 PM 96760 16329056 99.41 283440 14770392 7187548 1005592 12.27 23924
11:45:01 PM 94872 16330944 99.42 283480 14770532 7187548 1005592 12.27 23924
11:46:01 PM 95392 16330424 99.42 283520 14770680 7187548 1005592 12.27 23924
11:47:01 PM 90196 16335620 99.45 283568 14776592 7187548 1005592 12.27 23924
11:48:01 PM 91524 16334292 99.44 283596 14778728 7187548 1005592 12.27 23924
11:49:01 PM 91256 16334560 99.44 283648 14778792 7187552 1005588 12.27 23920
11:50:01 PM 92560 16333256 99.44 283712 14778824 7187552 1005588 12.27 23920
11:51:01 PM 90748 16335068 99.45 283772 14778912 7187552 1005588 12.27 23920
11:52:01 PM 91484 16334332 99.44 283800 14779068 7187552 1005588 12.27 23920
11:53:01 PM 89964 16335852 99.45 283844 14779136 7187572 1005568 12.27 23944
11:54:01 PM 80092 16345724 99.51 283980 14790212 7187572 1005568 12.27 23944
11:55:01 PM 72728 16353088 99.56 284052 14792660 7187572 1005568 12.27 23944
11:56:01 PM 72300 16353516 99.56 284092 14792844 7187612 1005528 12.27 23936
11:57:01 PM 72264 16353552 99.56 284152 14792908 7187612 1005528 12.27 23936
11:58:01 PM 73680 16352136 99.55 284248 14793040 7187612 1005528 12.27 23936
11:59:01 PM 73836 16351980 99.55 284300 14793172 7187612 1005528 12.27 23936
Average: 71240 16354576 99.57 265982 14818731 7172819 1020321 12.45 23450