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Don Burleson Blog 







The asmcmd Utility

Oracle Database Tips by Donald Burleson

A new command line tool is included with 10g release 2 called asmcmd.  Figure 11.3 shows that it is launched by first setting the environment for +ASM, then calling it with the asmcmd command. The idea of this tool is to make administering the asm files similar to administering standard operating system files.

Two Methods for Deleting Orphaned ASM Files

The asmcmd is a great tool for deleting orphaned files; files left over from previously dropped tablespaces. We have learned that if a datafile is created using only the diskgroup name, it will be automatically deleted if the tablespace is dropped. However, if a datafile is explicitly named, and its tablespace is dropped, it will become orphaned, taking up unnecessary space with no purpose. 

Figure 11.4 demonstrates creating a new tablespace with two named datafiles and then dropping it.

Now, there are two files stored on ASM that need to be deleted. This gives us the opportunity to remove these files with two different methods. The first method is the only method available in 10g release 1.

Figure 11.5 demonstrates deleting one file using sqlplus connected to the +ASM1 instance.

Figure 11.6 demonstrates deleting a file using asmcmd. Of course, this method is only available after 10g release 2 software is installed.

The asmcmd utility does not provide a command history with the up-arrow key. With rlwrapinstalled, this can be fixed by adding the following entry to the ~oracle/.bashrc file:

alias asmcmd='rlwrap asmcmd'

Creating a Database with Database Configuration Assistant

With the ASM instances running on both nodes, try creating an ASM dependant database with dbca. During this attempt, the message seen in Figure 11.7 will appear.

This is odd. The ASM instance is running but it is not detected! This never happened with release 1 software, so what has happened?

The problem is caused by the entry in the /etc/oratab file where ASM is listed using its database name instead of the instance name. Edit the file as in this example for oracle1:


Keep in mind that with this change, racenv cannot be used to change the environment to connect to +ASM. Use oraenv instead. 

Another consistent problem that has been experienced with the release 2 dbca is the error seen in Figure 11.8.

To fix this problem, simply run the script on each node to populate the tnsnames.ora in the release 2 home before database creation begins. It is not necessary to restart dbca to fix this problem. Click abort and start database creation anew. When the database is finished, edit the tnsnames.ora to check that all service entries are properly written.

An important new feature of dbca release 2 is the ability to configure only ASM. In release 1, it had to be done manually or as part of creating a database. This feature can be accessed from the screen depicted in Figure 11.9.

Learn More about PC RAC:

If you want to learn RAC at home, get the bestselling book "Personal Oracle Real Application Clusters" by Edward Stoever.

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



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