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Unix Utility - Fuser

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.


An UNIX utility, known as fuser, verifies if a file is open or closed. If an archive log is being written, UNIX will allow it to be copied, deleted, or have just about anything else done to it. Therefore, using fuser before copying an archive file will ensure all files are complete and usable for recovery. Any script written on a UNIX or Linux box for copying archive logs should use fuser to verify that a log is not being written before attempting to copy it.

About the only advantage of the raw configuration is the ability to parallel the archive log portion of the backup, if multiple tapes, one on each node, are used.

If only a single tape drive is available, the NFS mount scheme must be used. If the NFS mount is lost along with archive logs, the database may not be fully recoverable.

The initialization parameters should be set similar to:

ault1.LOG_ARCHIVE_DEST_1="LOCATION=/u01/backup/ault_rac1"
ault2.LOG_ARCHIVE_DEST_1="LOCATION=/u01/backup/ault_rac2"

By using the NFS mount scheme, either node can backup the archive logs in the other. On Linux, an explanation of the process to set up an NFS-mounted drive follows.

Configure the services such that the NFS services are running:

NFS
NFSLOCK
NETFS

Figure 13.4 shows the Service Configuration GUI with these services checked.

Figure 13.4: Service Configuration Screen with NFS services selected.

The NFS server must be configured on each node. Figure 13.5 shows the NFS Server GUI configuration screen for Linux.

Figure 13.5: Example NFS Configuration Screen

The root user performs the configuration for NFS mounts as follows.

1. On each RAC node, create the mount point directory exactly as it appears on each remote node. For example, for the server AULTLINUX2, the command to create the mount directory for the archive directory on AULTLINUX 1 would be:

$ mkdir /usr/backup/ault_rac1/archives1

2.  On each RAC node, the MOUNT command would be used to mount the NFS drive(s) from the other nodes. This is done using the mount directory created in the previous step. The example setup would be:

$ mount aultlinux1:/usr/backup/ault_rac2/archives2 /usr/backup/ault_rac2/archives2

Once the directories are cross-mounted, the process can then continue.

The configuration of NFS mount points on Solaris 9 would be done using manual commands:

1. Start the NFS server:

# /etc/init.d/nfs.server start

2. Set up the shares:

# share -F nfs -o rw=v10gsolaris2 /usr/backup/ault_rac1/archives1

3. Verify the shares are available on the target box:

# dfshares -F nfs v10gsolaris1

RESOURCE    SERVER                      ACCESS                     TRANSPORT

V10gsolaris1:/usr/backup/ault_rac1/archives1   v10gsolaris1-

4. On the target box, start the NFS client:

# /etc/init.d/nfs.client start

5. On the target box, create the required mount directory:

# mkdir /usr/backup/ault_rac1/archives1

6. On the target, mount the shared directory:

# mount -F nfs -o rw v10gsolaris1:/usr/backup/ault_rac1/archives1

Make sure the mount directory is created with the owner and group that will have access to the cross-mounted directory tree.

In Windows2000, the drives are shared across the network to achieve the same functionality.

The log_archive_format parameter determines the format of the archive logs that have been generated. It must be the same on all clustered nodes. The format strings allowed for log_archive_format are:

%T -- Thread number, left-zero-padded so LOG_ARCHIVE_FORMAT = ault_%T would be ault_0001

%t -- Thread number, non-left-zero-padded so LOG_ARCHIVE_FORMAT = ault_%t would be ault_1

%S -- Log sequence number, left-zero-padded, so LOG_ARCHIVE_FORMAT = ault_%S would be ault_0000000001

%s -- Log sequence number, non-left-zero_padded, so LOG_ARCHIVE_FORMAT = ault_%s would be ault_1.

The format strings can be combined to show both thread and sequence number. The %T or %t parameters are required for RAC archive logs.

In order to perform a complete recovery, a database, whether it is a normal database or a RAC database, must use archive logging. In order to turn on archive logging in RAC, the following procedure should be used:

1. Shut down all instances associated with the RAC database.

2. Choose one instance in the RAC cluster. In its unique initialization parameter file set the cluster_database parameter to false.  If a server parameter file is being used, <sid.> should be appended to the parameter.

3. In the instance parameter file, the log_archive_dest_n, log_archive_format and log_archive_start parameters should be set for the example instances:

v10g2.LOG_ARCHIVE_DEST_2 = "LOCATION=/u01/backup/ault_rac2 MANDATORY"
LOG_ARCHIVE_FORMAT = ault_%T_%s
LOG_ARCHIVE_START = TRUE

4. Start the instance.

$ sqlplus /nolog
SQL> connect / as sysdba

Connected to an idle instance

SQL> startup

<normal startup messages>

5. Execute the following command from the SQL*PLUS session:

SQL> alter database archivelog;

Command executed.

6. Shut down the instance.

7. Edit the instance initialization parameter file or server parameter file to reset cluster_database to TRUE.

8. Restart the instances.

 


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.

http://www.rampant-books.com/book_2004_1_10g_grid.htm


 

 
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