当数据库在nomount，mount或者restricted这类特殊状态下，同时动态监听显示状态为BLOCKED，客户端无法直接连接到实例，此时可通过配置UR=A进行连接。最常见的场景就是10g版本的RAC,配置OGG时需要访问ASM实例的情况（实测11.2版本的RAC ASM实例动态监听的显示状态为Ready，无需添加UR=A配置即可连接）。下面是测试过程：
1.测试10.2.0.5连接ASM
**环境：**Oracle 10.2.0.5 RAC + ASM tnsnames.ora配置如下：ASM =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.171)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = +ASM)
(INSTANCE_NAME = +ASM1)
)
监听状态如下：
[oracle@rac1-server admin]$ lsnrctl status
LSNRCTL for Linux: Version 10.2.0.5.0 - Production on 14-FEB-2019 19:37:22
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias LISTENER_RAC1-SERVER
Version TNSLSNR for Linux: Version 10.2.0.5.0 - Production
Start Date 12-FEB-2019 12:59:06
Uptime 2 days 6 hr. 38 min. 15 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /s01/oracle/product/10.2.0/db_1/network/admin/listener.ora
Listener Log File /s01/oracle/product/10.2.0/db_1/network/log/listener_rac1-server.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.172)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.171)(PORT=1521)))
Services Summary...
Service "+ASM" has 1 instance(s).
Instance "+ASM1", status BLOCKED, has 1 handler(s) for this service...
Service "+ASM_XPT" has 1 instance(s).
Instance "+ASM1", status BLOCKED, has 1 handler(s) for this service...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "SYS$SYS.KUPC$S_1_20170912101328.JY.ORACLE.COM" has 1 instance(s).
Instance "jy2", status READY, has 1 handler(s) for this service...
Service "jy.oracle.com" has 1 instance(s).
Instance "jy2", status READY, has 1 handler(s) for this service...
Service "jyXDB.oracle.com" has 1 instance(s).
Instance "jy2", status READY, has 1 handler(s) for this service...
Service "jy_XPT.oracle.com" has 1 instance(s).
Instance "jy2", status READY, has 1 handler(s) for this service...
Service "orcl" has 2 instance(s).
Instance "orcl1", status READY, has 2 handler(s) for this service...
Instance "orcl2", status READY, has 1 handler(s) for this service...
Service "orclXDB" has 2 instance(s).
Instance "orcl1", status READY, has 1 handler(s) for this service...
Instance "orcl2", status READY, has 1 handler(s) for this service...
Service "orcl_XPT" has 2 instance(s).
Instance "orcl1", status READY, has 2 handler(s) for this service...
Instance "orcl2", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@rac1-server admin]$
此时如果通过网络连接ASM实例，会报错ORA-12528：
[oracle@rac1-server admin]$ sqlplus sys/oracle@asm as sysdba
SQL*Plus: Release 10.2.0.5.0 - Production on Thu Feb 14 19:25:52 2019
Copyright (c) 1982, 2010, Oracle. All Rights Reserved.
ERROR:
ORA-12528: TNS:listener: all appropriate instances are blocking new connections
Enter user-name:
修改tnsnames.ora，增加UR=A配置：
ASM =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.171)(PORT = 1521))
(CONNECT_DATA =
(UR=A)
(SERVER = DEDICATED)
(SERVICE_NAME = +ASM)
(INSTANCE_NAME = +ASM1)
)
再次尝试通过网络连接ASM实例，可成功连接：
[oracle@rac1-server admin]$ sqlplus sys/oracle@asm as sysdba
SQL*Plus: Release 10.2.0.5.0 - Production on Thu Feb 14 19:26:26 2019
Copyright (c) 1982, 2010, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
SQL>
2.测试11.2.0.4连接ASM
**环境：**Oracle 11.2.0.4 RAC + ASM tnsnames.ora配置如下：ASM =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.107)(PORT = 1522))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = +ASM)
(INSTANCE_NAME = +ASM1)
)
)
监听状态如下：
[grid@db01 admin]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 14-FEB-2019 19:41:59
Copyright (c) 1991, 2013, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.4.0 - Production
Start Date 13-FEB-2019 11:28:44
Uptime 1 days 8 hr. 13 min. 14 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /opt/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /opt/app/grid/diag/tnslsnr/db01/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.107)(PORT=1522)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.117)(PORT=1522)))
Services Summary...
Service "+ASM" has 1 instance(s).
Instance "+ASM1", status READY, has 1 handler(s) for this service...
Service "A" has 1 instance(s).
Instance "orcl1", status READY, has 1 handler(s) for this service...
Service "B" has 1 instance(s).
Instance "orcl1", status READY, has 1 handler(s) for this service...
Service "orcl" has 1 instance(s).
Instance "orcl1", status READY, has 1 handler(s) for this service...
Service "orclXDB" has 1 instance(s).
Instance "orcl1", status READY, has 1 handler(s) for this service...
The command completed successfully
[grid@db01 admin]$
在没有配置UR=A的情况下，就可以正常连接到ASM实例：
--没有指定as sysasm会报错ORA-15000：
[oracle@db01 admin]$ sqlplus sys/oracle@asm
SQL*Plus: Release 11.2.0.4.0 Production on Thu Feb 14 19:23:57 2019
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-15000: command disallowed by current instance type
Enter user-name: ^C
--指定后就可以正常连接：
[oracle@db01 admin]$ sqlplus sys/oracle@asm as sysasm
SQL*Plus: Release 11.2.0.4.0 Production on Thu Feb 14 19:24:00 2019
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Real Application Clusters and Automatic Storage Management options
SQL>
由此验证了11.2.0.4环境下，通过网络连接ASM实例，不再需要UR=A的配置。