Large File Support with Fileshare

Fileshare, by default, supports files that can be up to 32 Terabytes in size.

An alternative technology, file striping, was introduced in previous releases as an interim solution to overcome limitations on the maximum allowed file size some operating systems permit. It enables you to specify that a single data file is to be stored in multiple physical files (or stripes) on disk.

Because of the complications involved with configuring striping together with Fileshare (these issues are discussed below), we recommend that you keep your large files non-striped and instead, configure the file handler to use its standard large file support.

To configure large file support under Fileshare, you should consider the following:

• Location of the extfh.cfg file

  The extfh.cfg file must be located in the same directory as the Fileshare Server or, if the EXTFH environment variable has been set to point to the extfh.cfg file, it must have been set in the Fileshare Server session.

• Switching on large file support

  Makes sure the value of FILEMAXSIZE specified in the extfh.cfg file is 8. This is the default value.

The following information explains how to configure striped files under Fileshare control if your operating system does not support large files:

• Expanded filenames in the extfh.cfg file

  You must use the fully qualified name of the base file in the extfh.cfg configuration file. This name includes the pathnames that you can see if you press F2 at the Fileshare Server to switch tracing on.

  UNIX:

  For example, on UNIX:

  [/u/username/file.dat]
  Striping=on

  Note:

  You need only do this for files accessed through Fileshare. To enable the file handler to find the setting in extfh.cfg the filename tag must match exactly that specified by the I/O request, which in the case of Fileshare includes a fully qualified path.

• Backslash character

  The backslash character is treated as an escape character within the extfh.cfg file.

  Windows:

  On Windows platforms you must therefore specify two backslash characters for each backslash character in the pathname, for example:

  [d:\\fsrvr\\file.dat]
  Striping=on

• Alternate filenames

  You can specify file striping on an alternate filename (specified in the database reference file using filename mapping). In this case, the expanded filename is not required. For example, if the database reference file contains the following line:

  /f file1.dat /af file2.dat

  you can specify the following in the extfh.cfg file:

  [file2.dat]  
  Striping=on

• StripeNameType

  StripeNameType=1 (the default is StripeNameType=0) only works with Fileshare if the base filename does not have an extension. If you specify StripeNameType=1 for a filename that has an extension, the file is created but it is not striped.

• Back up and recovery

  The use of striping complicates the process of logging for rollforward recovery because the administrator has to ensure that the correct versions of the files are in the latest backup, and that they are correctly restored in the event of needing to run the Fileshare Recovery Utility. This process is much more complex if file stripes also have to be maintained.

  The Automatic Database Backup and Recovery facility does not work correctly on striped files because it uses low-level I/O routines for backups and restores which are unaware of the stripe configuration.

• Not using Fileshare

  The filenames passed to the File Handler must match exactly so that the File Handler can locate the filename tags in the extfh.cfg file.

  Generally, only Fileshare passes fully qualified names. Therefore, if you have set up an extfh.cfg file for use under Fileshare with expanded pathnames and then want to access the files outside of Fileshare, you need to change the filename tags in extfh.cfg to match exactly the filenames passed by the application.