Size limits on VOB elements

Answer

Starting with ClearCase 7.0 and with a minimum feature level of 5, ClearCase added Large File Support (LFS).

ClearCase type managers are responsible for maintaining the storage of checked in versions.  Some type managers maintain an individual file ("source container") for each checked in version.  Others compress the contents of checked in versions and may store more than one version in a single source container.  Built-in and customer-created element types must specify which type manager the element type is to use.

Type managers that support LFS

- whole_copy
The whole_copy type manager stores the contents of each checked in version in a separate source container.  Versions of element types using whole_copy may be as large as the underlying file system supports.

- z_whole_copy (whole copy with compression):
The z_whole_copy type manager stores the contents of each checked in version in a separate source container.  Versions of element types using z_whole_copy may be as large as the underlying file system supports.

- text_file_delta
The text_file_delta type manager stores the contents of all versions of the element in a single source container.  Individual versions must be less than 2GB but the source container may grow as large as the underlying file system supports.

- z_text_file_delta (text_file_delta with source container compression)
The z_text_file_delta type manager stores the contents of all versions of the element in a single source container.  Individual versions must be less than 2GB but the source container may grow as large as the underlying file system supports.

Type manager inheritance

Some other type managers inherit the container management of the LFS type managers that are listed above.  These type managers have the same file size characteristics as the type manager from which they inherit container management.  For example, the _ms_word type manager inherits container management from z_whole_copy.  Thus, versions of element types using _ms_word may be as large as the underlying file system supports.

On Unix or Linux, you can determine which container management is used by a type manager by running ls -l on the 'construct_version' file in each type manager directory under $CLEARCASE_HOME/lib/mgrs. On Windows, you can determine which container management is used by a type manager by examining the 'construct_version' entry for each type manager in the %CLEARCASE_HOME%\lib\mgrs\map file.

Determining the type manager of an element type

You can determine the type manager used by each element type in a VOB by running cleartool lstype -kind eltype.

ClearCase LFS and native filesystems

LFS is available on all operating systems. The underlying file system sets the limit. Not all platforms have a default configuration that supports files of that size. On hosts that run UNIX or Linux, use the ulimit(1) command to obtain or set the maximum file size.

ClearCase was tested with files as large as 68 Gb. If you plan to use large files, consider testing with files as large as you plan to store. If a problem occurs, contact IBM Support to investigate and find the root cause.