ORA-12545: Connect failed because target host or object does not exist

11.2.0.4的  data guard，配制了broker，从主库切换到备库的时候，正常。再从备库切换到主库的时候。出现问题。

DGMGRL> switchover to testogg;
Performing switchover NOW, please wait...
Operation requires a connection to instance "testogg" on database "testogg"
Connecting to instance "testogg"...
Connected.
New primary database "testogg" is opening...
Operation requires startup of instance "testogg_stdby" on database "testogg_stdby"
Starting instance "testogg_stdby"...
Unable to connect to database
ORA-12545: Connect failed because target host or object does not exist

Failed.
Warning: You are no longer connected to ORACLE.

Please complete the following steps to finish switchover:
	start up instance "testogg_stdby" of database "testogg_stdby"

DGMGRL> 

查看alert log日志，提示log_archive_dest_2 是invalid的 。并且提示db_unique_name不对。

Switchover: Primary highest seen SCN set to 0x0.0x1a410d
ARCH: Noswitch archival of thread 1, sequence 113
ARCH: End-Of-Redo Branch archival of thread 1 sequence 113
ARCH: LGWR is actively archiving destination LOG_ARCHIVE_DEST_3
ARCH: Standby redo logfile selected for thread 1 sequence 113 for destination LOG_ARCHIVE_DEST_3
Archived Log entry 32 added for thread 1 sequence 113 ID 0xe0779467 dest 1:
ARCH: Archiving is disabled due to current logfile archival
Primary will check for some target standby to have received alls redo
Final check for a synchronized target standby. Check will be made once.
Archive destination LOG_ARCHIVE_DEST_2 invalidated
DB_UNIQUE_NAME tesgogg is not in the Data Guard configuration
LOG_ARCHIVE_DEST_3 is a potential Physical Standby switchover target
Active, synchronized target has been identified
Target has also received all redo

检查log_archive_dest_2的设置，发现db_unique_name的确有问题，更改，提示和log_archive_dest_3因为值相同有冲突。

SYS@testogg_stdby>alter system set log_archive_dest_2= 'SERVICE=tesgogg ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=testogg';
alter system set log_archive_dest_2= 'SERVICE=tesgogg ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=testogg'
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-16021: session LOG_ARCHIVE_DEST_3 destination cannot be the same as session
LOG_ARCHIVE_DEST_2 destination

查看log_archive_dest_3,发现的确配置了log_archive_dest_3。但是搭建data guard的时候，并没有设置这个参数。该参数是配置broker后，broker自己生成的。清空后，设置log_archive_dest_2.

SYS@testogg_stdby>show parameter log_archive_dest_3

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest_3		     string	 service="testogg", LGWR ASYNC
						 NOAFFIRM delay=0 optional comp
						 ression=disable max_failure=0
						 max_connections=1 reopen=300 d
						 b_unique_name="testogg" net_ti
						 meout=30, valid_for=(all_logfi
						 les,primary_role)
log_archive_dest_30		     string
log_archive_dest_31		     string
SYS@testogg_stdby>alter system set log_archive_dest_3='';

System altered.

SYS@testogg_stdby>alter system set log_archive_dest_2= 'SERVICE=tesgogg ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=testogg';

System altered.

设置完毕后，还是存在无法切换data guard的问题。检查broker的配置。发现数据库的配置中，连接的host是hostname，而不是IP地址。

DGMGRL> show database verbose testogg_stdby;

Database - testogg_stdby

  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   (unknown)
  Apply Lag:       (unknown)
  Apply Rate:      (unknown)
  Real Time Query: OFF
  Instance(s):
    testogg_stdby

  Properties:
    DGConnectIdentifier             = 'testogg_stdby'
    ObserverConnectIdentifier       = ''
    LogXptMode                      = 'ASYNC'
    DelayMins                       = '0'
    Binding                         = 'OPTIONAL'
    MaxFailure                      = '0'
    MaxConnections                  = '1'
    ReopenSecs                      = '300'
    NetTimeout                      = '30'
    RedoCompression                 = 'DISABLE'
    LogShipping                     = 'ON'
    PreferredApplyInstance          = ''
    ApplyInstanceTimeout            = '0'
    ApplyParallel                   = 'AUTO'
    StandbyFileManagement           = 'AUTO'
    ArchiveLagTarget                = '0'
    LogArchiveMaxProcesses          = '4'
    LogArchiveMinSucceedDest        = '1'
    DbFileNameConvert               = '/u01/app/oracle/oradata/testogg/, /u01/app/oracle/oradata/testogg_stdby/'
    LogFileNameConvert              = '/u01/app/oracle/oradata/testogg/, /u01/app/oracle/oradata/testogg_stdby/'
    FastStartFailoverTarget         = ''
    InconsistentProperties          = '(monitor)'
    InconsistentLogXptProps         = '(monitor)'
    SendQEntries                    = '(monitor)'
    LogXptStatus                    = '(monitor)'
    RecvQEntries                    = '(monitor)'
    ApplyLagThreshold               = '0'
    TransportLagThreshold           = '0'
    TransportDisconnectedThreshold  = '30'
    SidName                         = 'testogg_stdby'
    StaticConnectIdentifier         = '(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=dbtrain)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=testogg_stdby_DGMGRL)(INSTANCE_NAME=testogg_stdby)(SERVER=DEDICATED)))'
    StandbyArchiveLocation          = '/archive_log/'
    AlternateLocation               = ''
    LogArchiveTrace                 = '0'
    LogArchiveFormat                = '%t_%s_%r.dbf'
    TopWaitEvents                   = '(monitor)'

Database Status:
DGM-17016: failed to retrieve status for database "testogg_stdby"
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
ORA-16625: cannot reach database "testogg_stdby"

DGMGRL> 

检查主备库的hosts文件，发现里面没有对方的地址。添加。再次在dgmgrl命令行下执行切换。主备切换正常。

DGMGRL> switchover to testogg
Performing switchover NOW, please wait...
Operation requires a connection to instance "testogg" on database "testogg"
Connecting to instance "testogg"...
Connected.
New primary database "testogg" is opening...
Operation requires startup of instance "testogg_stdby" on database "testogg_stdby"
Starting instance "testogg_stdby"...
ORACLE instance started.
Database mounted.
Database opened.
Switchover succeeded, new primary is "testogg"

END