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FairCom ISAM for C

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File Size and Operating System Limits

Different platforms support different maximum file sizes. The limit is imposed by the data type for the value used to seek to a given offset in a file. Older operating systems use a 4-byte signed offset, allowing physical files up to 2 GB. Newer platforms use 4-byte unsigned offsets (4 GB) or 8-byte unsigned offsets (16,000,000 terabytes = 18 exabytes).

On systems supporting only 4-byte signed offsets:

  • Standard c-tree files can grow up to 2 GB in size.
  • Extended files (also referred to as "huge" files) can be segmented into multiple physical files up to 2 GB each, allowing a single logical file to grow:
    • To 4 GB using only segmented file support (using segments <= 2 GB each)
    • Up to 16,000,000 terabytes using segmented file support and huge file support (using segments <= 2 GB each)

The following platforms are limited to 2 GB files:

AT&T SVR4

SunOS

HP-UX 10

IBM AIX 3.2-4.1

Linux (before kernel 2.400)

SCO OpenServer/UnixWare

Macintosh (7-9, OS X)

QNX 2 & 4

 

On systems supporting a 4-byte unsigned offset:

  • Standard c-tree files can grow up to 4 GB in size.
  • Extended files using huge file support and segmented file support can grow to 18 exabytes (using segments <= 4 GB each).

The following platforms fall into this category:

Windows 95 and 98 - FAT file system

Solaris 2.6 (Intel/SPARC)

On systems supporting 8-byte offsets:

  • Extended format files with huge file support can grow up to 18 exabytes.
  • Segmented file support is optional, but convenient for allocating portions of files to different volumes.
  • Standard c-tree files can grow up to 4 GB in size.

The following platforms fall into this category:

Windows NT/2000 and above - NTFS file system

HP-UX 11

AIX 4.2 and above

Solaris 7 and above (Intel and SPARC)

Linux (kernel 2.400 or later)

FreeBSD

File Handles/Descriptors

FairCom DB must request a file handle (file descriptor) for each file it has open.

The number of concurrent file handles is limited to 32768.

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