Oracle RAC Dump Area Test

Trace files, typically used for troubleshooting issues with key database operations, are stored in dump area destinations marked for every such operation. For instance, a background dump destination can be specified using the BACKGROUND_DUMP_DEST initialization parameter in Oracle; trace files for the background processes are written to this destination only. Similarly, trace files for user processes are generated and stored in the user dump destination, which is set using the USER_DUMP_DEST parameter in Oracle.

The dump destinations so created should be adequately sized, so that there is always enough space in the destination directory for storing trace files. If any of the destination directories become full, then trace files cannot be created for the corresponding database operation; while the absence of trace files can make debugging difficult, in some cases, it can even bring the database operations to a standstill. 

In order to avoid such anomalies, the usage of each dump destination should be monitored, and administrators promptly alerted to space inadequacies, so that required space is made available in the dump directory. The Oracle RAC Dump Area test serves this purpose effectively. This test runs periodic checks on the usage of every dump destination that has been configured for monitoring, and alerts administrators if any of the configured dump destinations or dump drives are likely to run out of space.

Note:

For this test to work, the eG install user should be in the Oracle User Group.

Target of the test : An Oracle Cluster

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every dumpfile that is auto-discovered on the target Oracle Cluster being monitored.

Configurable parameters for the test
Parameter Description

Test period

How often should the test be executed

Host

The host for which the test is to be configured.

Port

The port on which the server is listening.

Service Name

A ServiceName exists for the entire Oracle RAC system. When clients connect to an Oracle cluster using the ServiceName, then the cluster routes the request to any available database instance in the cluster. By default, the Service Name is set to none. In this case, the test connects to the cluster using the ORASID and pulls out the metrics from that database instance which corresponds to that ORASID. If a valid service name is specified instead, then, the test will connect to the cluster using that Service Name, and will be able to pull out metrics from any available database instance in the cluster.

To know the Service Name of a cluster, execute the following query on any node in the target cluster:

select name, value from v$parameter where name =’service_names’

ORASID

The variable name of the oracle instance.

Username

In order to monitor an Oracle database server, a special database user account has to be created in every Oracle database instance that requires monitoring. A Click here hyperlink is available in the test configuration page, using which a new oracle database user can be created. Alternatively, you can manually create the special database user. When doing so, ensure that this user is vested with the select_catalog_role and create session privileges.

The sample script we recommend for user creation (in Oracle database server versions before 12c) for eG monitoring is:

create user oraeg identified by oraeg

create role oratest;

grant create session to oratest;

grant select_catalog_role to oratest;

grant oratest to oraeg;

The sample script we recommend for user creation (in Oracle database server 12c) for eG monitoring is:

alter session set container=<Oracle_service_name>;

create user <user_name>identified by <user_password> container=current default tablespace <name_of_default_tablespace> temporary tablespace <name_of_temporary_tablespace>;

Grant create session to <user_name>;                                

Grant select_catalog_role to <user_name>;

The name of this user has to be specified here.

Password

Specify the password of the specified database user.

Confirm Password

Confirm the Password by retyping it here.

DumpFilePath

By default, the eG agent auto-discovers the name and full path to all dump destinations on the target Oracle Cluster database server. This is why, the DumpFilePath parameter is set to none by default. If required, you can manually specify the path to the dump destination to be monitored. For eg, /user/john/udump. In this case , multiple paths can also be provided as a comma-separated list - e.g., /user/john/udump, /user/john/bdump.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Used Dump area

Indicates the amount of space in this dump destination that is currently occupied by trace files.

MB

 

Used drive space

Indicates the space in the dump drive that is currently occupied by all files, including trace files.

MB

 

 

Relative dump area usage

Indicates the percentage of the total used space in the dump drive that is occupied by trace files.

Percent

This measurement value should ideally be below 50%. Any value higher than 50%, indicates that the trace files are consuming more space than the other files in the dump drive. To free some space in that drive,  you can adopt any of the following approaches:

  • Add more disk space to the dump drive;
  • Take backups of the old trace files to tape or to another destination, and remove them from the dump drive;
  • Temporarily, you can even zip all trace files in the dump destination.

If sufficient space is not made available to the dump destination soon, then trace files can no longer be created in the directory; sometimes, this can cause the Oracle instance to fail.

Available drive space

Indicates the available free space in the dump drive.

MB

 

Free drive space

Indicates the percentage of space in the dump drive that is currently unused.

Percent

This measurement value should ideally be high. If the value is consistently low, you may want to check the value of the Relative dump area usage measure to determine what is causing the space drain - is it because of the trace files, or the other files in the dump destination drive? If the trace files appear to be consuming excessive space in the drive, you can free some space in the drive by adopting any of the following approaches:

  • Add more disk space to the dump drive;
  • Take backups of the old trace files to tape or to another destination, and remove them from the destination directory;
  • Temporarily, you can even zip all trace files in the dump drive.

Dump area growth

Indicates the rate at which  dump files are eroding the space in the dump drive.

MB/Sec

Ideally, the value of this measure should be low. A consistent increase in this value is a cause for concern as it indicates that free space in the dump drive is getting eroded at a rapid pace. This in turn hints at a potential space crunch in the directory, which if not averted, could cause the performance of the database server to deteriorate.