Understanding the nvfail option

How Data ONTAP provides database file protection

Data ONTAP provides database file protection through the nvfail option of the vol options command. The nvfail option enables Data ONTAP to detect nonvolatile RAM (NVRAM) inconsistencies at boot time or while taking over in a cluster failover configuration.You use it to warn database administrators of NVRAM problems that can compromise database validity. If Data ONTAP finds any problems, database instances stop responding or shut down, and Data ONTAP sends error messages to the console to alert you to check the state of the database.

How to provide additional protection for database files

You can provide additional protection to specific database files by adding them to an optional file you create called /etc/nvfail_rename. When you enable nvfail and Data ONTAP detects NVRAM errors at bootup, Data ONTAP renames any database files specified in the nvfail_rename file by appending .nvfail to the original file name. When Data ONTAP renames a database file, the database cannot restart automatically. This gives you the opportunity to examine the file for inconsistencies before you remove the .nvfail extension and make the file accessible again.

How nvfail works

When you enable nvfail, one of the following processes takes place during bootup.

If Data ONTAP...	Then...
Detects no NVRAM errors	File service starts normally.
Detects NVRAM errors and you use the optional nvfail_rename file	Data ONTAP returns a stale file handle (ESTALE) error to NFS clients trying to access the database, causing the application to stop responding, crash, or shut down. Data ONTAP then sends an error message to the filer console and log file. Data ONTAP renames database files specified in the nvfail_rename file by appending .nvfail to the original file names, making those files unavailable to both CIFS and NFS clients.
Detects NVRAM errors and you do not use the optional nvfail_rename file	Data ONTAP returns a stale file handle (ESTALE) error to NFS clients trying to access the database, causing the application to stop responding, crash, or shut down. Data ONTAP then sends an error message to the filer console and log file. No database files are renamed. When the application restarts, files are available to CIFS clients, even if you have not verified that they are valid. For NFS clients, files remain inaccessible as long as the file system is not remounted, independent of the application restarting.

Where to look for database file verification instructions

See the documentation for your specific database software for instructions about examining database file validity.