ASM调整memory内存参数小于1G失效，测试环境安装19c,内存不太够，需要降低asm 内存参数，但是发现调整后未生效.总结下，oracle 11.2.0.4 >=oracle 建议是asm内存是最低1G，如果配置小于这个数值，会自动调整为1G大小.

1.查看当前的memory

SQL>show parameter memory
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
memory_max_target                    big integer 1076M
memory_target                        big integer 1076M

2.修改memory参数，并重启查看

SQL> alter system set memory_max_target=400m scope=spfile sid='+ASM1';
SQL> alter system set memory_target=400m scope=spfile sid='+ASM1';

重启ASM实例后,Memory_target参数无变化，且数据库未报错。
$ srvctl stop asm -n c1 -stopoption IMMEDIATE -force
$ srvctl start asm -n c1
SQL>show parameter memory
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
memory_max_target                    big integer 1076M
memory_target                        big integer 1076M

SQL> alter system set memory_max_target=400m scope=spfile sid='+ASM1';
SQL> alter system set memory_target=400m scope=spfile sid='+ASM1';

3.查看 ASM alert启动日志

Using parameter settings in server-side spfile +OCR/ora19c-cluster/ASMPARAMETERFILE/registry.253.1036510257
System parameters with non-default values:
large_pool_size = 12M
memory_target = 1G
memory_max_target = 1G

2019-04-01T06:47:45.260548-07:00
Domain name: user.slice
2019-04-01T06:47:45.260604-07:00
Per process system memlock (soft) limit = UNLIMITED
2019-04-01T06:47:45.260658-07:00
Expected per process system memlock (soft) limit to lock
instance MAX SHARED GLOBAL AREA (SGA) into memory: 1021M

4.查看官方文档Doc ID 1982132.1

总结下，oracle 11.2.0.4 >=oracle 建议是asm内存是最低1G，如果配置小于这个数值，会自动调整为1G大小！
以此类推oracle19c的asm内存最低也为1g，正常情况我们设置asm内存为2g
Default and Minimum MEMORY_TARGET & MEMORY_MAX_TARGET Value for ASM 11.2.0.4 and Onwards (Doc ID 1982132.1)