Learn about using Oracle Wallet in this section.

1. Create a directory for the wallet. For example:

   mkdir $ORACLE_HOME/oracle/wallet
   

2. Create an auto-login wallet.

   mkstore -wrl $ORACLE_HOME/oracle/wallet -create
   

3. Add the wallet location in the client's sqlnet.ora file:

   WALLET_LOCATION = (SOURCE = (METHOD = FILE) (METHOD_DATA = (DIRECTORY =
    $ORACLE_HOME/oracle/wallet) ) ) 
   

4. Add the following parameter in the client's sqlnet.ora file:

   SQLNET.WALLET_OVERRIDE = TRUE
   

5. Create credentials:

   mkstore -wrl wallet_location -createCredential db_connect_string username password
   

   For example:

   mkstore -wrl $ORACLE_HOME/oracle/wallet -createCredential DBConnectString scott password
   

6. Add the connection alias to your tnsnames.ora file.
7. Use dbfs_client with Oracle Wallet.

   For example:

   $ dbfs_client -o wallet /@DBConnectString /mnt/dbfs 

The dbfs_client program supports multiple levels of tracing to help diagnose problems.

The dbfs_client can either output traces to a file or to /var/log/messages using the syslog daemon on Linux.

When you trace to a file, the dbfs_client program keeps two trace files on disk. dbfs_client, rotates the trace files automatically, and limits disk usage to 10 MB.

By default, tracing is turned off except for critical messages which are always logged to /var/log/messages.

If dbfs_client cannot connect to the Oracle Database, enable tracing using the trace_level and trace_file options. Tracing prints additional messages to log file for easier debugging.

DBFS uses Oracle Database for storing files. Sometimes Oracle server issues are propagated to dbfs_client as errors. If there is a dbfs_client error, please view the Oracle server logs to see if that is the root cause.

The dbfs_client program can failover to one of the other existing database instances if one of the database instances in an Oracle RAC cluster fails.

exec DBMS_SERVICE.MODIFY_SERVICE(service_name => 'service_name',
              aq_ha_notifications => true,
              failover_method => 'BASIC',
              failover_type => 'SELECT',
              failover_retries => 180,
              failover_delay => 1);

The sharing and caching semantics for dbfs_client are similar to NFS in using the close-to-open cache consistency behavior.

You have two alternatives for backing up DBFS.

You can back up the tables that underlie the file system at the database level or use a file system backup utility, such as Oracle Secure Backup, through a mount point.

Topics:

• DBFS Backup at the Database Level
  An advantage of backing up the tables at the database level is that the files in the file system are always consistent with the relational data in the database.
• DBFS Backup Through a File System Utility
  The advantage of backing up the file system using a file system backup utility is that individual files can be restored from backup more easily.

Like any shared file system, the performance of DBFS for small files lags the performance of a local file system.

Each file data or metadata operation in DBFS must go through the FUSE user mode file system and then be forwarded across the network to the database. Therefore, each operation that is not cached on the client takes a few milliseconds to run in DBFS.

For operations that involve an input/output (IO) to disk, the time delay overhead is masked by the wait for the disk IO. Naturally, larger IOs have a lower percentage overhead than smaller IOs. The network overhead is more noticeable for operations that do not issue a disk IO.

When you compare the operations on a few small files with a local file system, the overhead is not noticeable, but operations that affect thousands of small files incur a much more noticeable overhead. For example, listing a single directory or looking at a single file produce near instantaneous response, while searching across a directory tree with many thousands of files results in a larger relative overhead. Oracle recommends direct_io option in dbfs_client for optimal performance for reads and writes.