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How To Collect The ACFS Metadata Using The "acfsutil meta" Command in Exadata, ODA, SuperCluster And Non-Engineered-Systems Environments (Doc ID 2313909.1)

Last updated on JUNE 04, 2023

Applies to:

Oracle Database Cloud Schema Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.


1) This document provide the steps and example about how to collect the ACFS metadata using the "acfsutil meta" command in Exadata, ODA, SuperCluster and Non-Engineered-Systems Environments.

2) "acfsutil meta" command copies metadata from an Oracle ACFS file system into a separate output file.

3) Syntax and Description:

acfsutil meta -h

acfsutil meta [-v] [-q] [-l log_file_path] [-o acfs_extent_offsets] {-f output_file} [-a <device>] volume_device


Option Description
-v Specifies verbose mode to generate additional diagnostic messages.
-q Invokes the metadata collector in quick mode.
-l log_file_path Specifies the path to the log file. If not specified, the log file is generated in the current directory with a default name of acfs.meta.log.
-o acfs_extent_offsets Specifies a list of comma separated file offsets from which the meta collector additionally copies data.
-f output_file Specifies the path name of the output file into which the metadata is copied.
-a device Specifies the location of any associated accelerator device, to be used if the file system is unmountable.
volume_device Specifies a volume device name of the file system which is to be copied.


4) The acfsutil meta command operates as a metadata collector to partially copy an Oracle ACFS file system into a separate specified output file. The metadata collector reads the contents of the file system specified by the volume device name of an Oracle ACFS file system. This input file system is searched for Oracle ACFS metadata and then all metadata found is written into the specified output file. The generated output file can be used for further diagnostics and analysis, without impact to the original file system at the customer site.

5) To obtain the best copy of the file system with acfsutil meta, unmount the file system before running acfsutil meta. If it is not possible to unmount the file system, avoid modifying the contents or performing a volume resizing operation while acfsutil meta is running.

6) If the original file system is very large, then the output file can also be very large*. The output file should be placed on a file system that supports sparse files because this placement can reduce the size of the file. When copying the output file, use a utility that supports sparse files. Compress the output file when possible to reduce storage space and transmission time.

*The ACFS filesystem for the sharedrepo can be 1.1 TB

As of 18.1 the 'acfsutil meta' command now generates a single smaller record oriented metadata file which can be expanded into metadata sparse files using "acfsutil meta -e metadata.file".
The expanded files can then be analyzed using fsck/acfschkdsk.

Reference: Bug 25764672  Diagnosibility-ACFS: Fix acfsutil meta to make a smaller internet safe output file (Doc ID 25764672.8)

7) If the file system has an accelerator device associated with it, acfsutil meta also copies the accelerator device data to a second output file. The second file uses the file name from the -f option with an appended .acc extension. For example, if you specify acfsutil meta -f /tmp/mymetafile volume1-123, the meta collector places a copy of volume1-123 in /tmp/mymetafile, and the copy of its accelerator device in the /tmp/mymetafile.acc file. This operation occurs automatically.

8) In most circumstances, acfsutil meta automatically copies the accelerator device to the second file. However, if you have think that the meta collector is not able to find the accelerator device on its own, you can specify the name on the command line with the -a option. For example, this situation could occur if the file system is corrupt. Note that using the -a option overrides how the meta collector operates automatically, so -a should be used carefully.

9) The output file should not be placed on the Oracle ACFS device that is specified as the input device because the metadata command might process the output file also. The output file should be placed on a file system that can support an output file which is the size of the Oracle ACFS input volume device.

10) The -q flag should be used with caution. When -q is specified, the meta collector does not scan and copy the entire input file system. Instead, it only scans and copies a predetermined number of bytes and certain data structures which are considered important. The primary use for the -q flag is for situations where there is not sufficient time to run the full version of the metadata collector. The -q flag should not be used unless it is recommended by the support personnel investigating the problem.

11) The acfsutil meta output file can be read by the acfsutil fsck command in most cases. However, the Oracle ACFS specific acfsutil fsck command on some OS platforms might not access the output file correctly or might not work with a specified flag. You can use a slightly modified fsck command form in these cases. For example:

On Linux, run the command in this format if you are using the -x flag:  



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