START OBSERVER

Format

START OBSERVER [<observer_name>] [FILE IS <observer_file>] [LOGFILE IS <observer_log_file>] [TRACE_LEVEL IS { USER | SUPPORT }];

Command Parameters

observer_name

A name to identify observers within the same Data Guard broker configuration.

No two observers on the same Data Guard broker configuration can have the same name.
If no name is specified for the observer then a default observer name, the host name of machine where the START OBSERVER command is issued, is used.
An observer name is case-insensitive.
The strings "NONAME" and "ALL" cannot be used as an observer name.

observer_log_file

Specifies the path and name of the runtime data file. If you specify only a file name, the path used is

$DG_ADMIN/config_ConfigurationSimpleName/dat

. If you omit both the path and file name, the file name defaults to fsfo_hostname.dat and the path is $DG_ADMIN/config_ConfigurationSimpleName/dat. If the DG_ADMIN environment variable is not defined, the default path is the current working directory.

log_file

The full path name of the observer log file. Each observer has its own log file.

Usage Notes

You can register up to four observers to monitor a single Data Guard broker configuration. Each observer is identified by a name that you supply when you issue the START OBSERVER command. See Installing and Starting the Observer.
The optional clause TRACE_LEVEL IS lets you control the amount of tracing done and written to the observer log file. The default value is USER, which limits the observer log contents to tracing information about fast-start failover, status changes of the primary and target standby database, and error/warning messages. Setting TRACE_LEVEL to SUPPORT increases the amount of tracing information to include lower-level information needed by Oracle Support Services.
The Oracle Client Administrator kit, or the full Oracle Database Enterprise Edition or Oracle Personal Edition kit must be installed on the observer computer to monitor a broker configuration for which fast-start failover is to be enabled. See Prerequisites for Enabling Fast-Start Failover for more information.
The START OBSERVER command must be issued on the observer computer. Once the observer is successfully started, control is not returned to the user until the observer is stopped (for example, by issuing the STOP OBSERVER command from a different client connection). If you want to perform further interaction with the broker configuration, you must connect through another client.

For information about how to start the observer in the background, see START OBSERVER IN BACKGROUND.
If the LOGFILE IS clause is used, then all observer output is recorded in the specified file. Observer output is useful for troubleshooting problems with the observer and with fast-start failover in general.

If a complete path, with file name, is provided, the file is stored in the specified path.

If only a file name is provided and the DG_ADMIN environment variable is defined, the specified file is stored in the $DG_ADMIN/config_ConfigurationSimpleName/log directory. If the DG_ADMIN environment variable is not defined, the file is stored in the current working directory.

If LOGFILE IS clause is omitted, the log file is stored in the $DG_ADMIN/config_ConfigurationSimpleName/log directory using the name observer_hostname.log. If the DG_ADMIN environment variable is not defined, the log file is stored as observer_hostname.log in the current working directory. ConfigurationSimpleName is the name of the broker configuration.

If the specified log file is not accessible, the observer output is sent to standard output.
If a complete directory path and file name is specified with the FILE IS clause, the observer runtime data file is created in this directory. If a relative path and file name is specified, the file is created in the specified path under the current working directory.

If only a file name is specified, the file is stored in the $DG_ADMIN/config_ConfigurationSimpleName/dat/ directory. If the DG_ADMIN environment variable is not defined, the file is stored in the current working directory. ConfigurationSimpleName, which is a configuration property, is the name of the broker configuration.

If this clause is omitted, the file is stored as $DG_ADMIN/config_ConfigurationSimpleName/dat/FSFO_hostname.dat. If the DG_ADMIN environment variable is not defined, the file is stored in the current working directory as fsfo.dat.
The primary and target standby database DB_UNIQUE_NAME initialization parameter and connect identifiers are stored in the fsfo.dat configuration file. Oracle recommends you ensure this file is protected from unauthorized access.
The order of the FILE IS, LOGFILE IS, and TRACE LEVEL IS clauses is interchangeable.
Fast-start failover does not need to be enabled before you issue this command.
- If fast-start failover is enabled, the observer will retrieve primary and target standby connect identifiers from the broker configuration and begin monitoring the configuration.
- If fast-start failover is not enabled, the observer continually monitors for when fast-start failover is enabled.
Only the primary database needs to be running when you issue this command; the standby database that will be the target of a fast-start failover does not need to be running in order for this command to complete successfully.
Use the SHOW OBSERVER command or the SHOW CONFIGURATION VERBOSE command, or query the V$FS_FAILOVER_OBSERVERS view on the primary database to see the status of the observer and its host computer.
If the primary and target standby databases stay connected but they lose the connection to the observer, then the primary database goes into an unobserved state. This state is reported by the broker's health check capability.
The SHOW OBSERVER command indicates whether one or more observers have already been started.

If the SHOW OBSERVER command shows one or more registered observers, but some of them are no longer running for some reason, then you can do either of the following:
- Issue the START OBSERVER command on the same observer computer where it was started originally, with the observer configuration file used when the observer was first started.
- Issue the STOP OBSERVER command and then the START OBSERVER command on any computer to start the observer.
If the SHOW OBSERVER command shows one or more observers and one observer is already running at one location, then an attempt to start an observer at that location again will fail with the following error:
```
Unable to open the observer file
```
If the SHOW OBSERVER command shows four registered observers and you attempt to start an observer at a different location, then the command will fail with the following error:
```
ORA-16647: could not start more than four observers
```

Command Examples

Example 1: Starting the Observer

The following example shows how to start the observer.

DGMGRL> CONNECT sysdg@North_Sales.example.com;
Password: password
Connected to "North_Sales"
Connected as SYSDG.
DGMGRL> START OBSERVER;
Observer started

Example 2: Starting the Observer Without Showing Credentials

The following example shows how to start the observer using CONNECT '/' so that connection credentials are not visible on the command line:

DGMGRL> CONNECT /@North_Sales.example.com;
Connected to "North_Sales"
DGMGRL> START OBSERVER;
Observer started.

You must set up Oracle Wallet or SSL to use CONNECT '/'. By setting up Oracle Wallet or SSL, you can write a script to securely start and run the observer as a background job without specifying database credentials in the script. When using Oracle Wallet as a secure external password store, be sure to add credentials for both the primary and fast-start failover target standby databases. The database connect string that you specify when adding the credentials for each database must match the ObserverConnectIdentifer or DGConnectIdentifier database property.