File system comparison

These tables summarize the features and limitations of each file system.

Table 1. File system summary (Part 1 of 2)
Capability "root" (/) QOpenSys QSYS.LIB16 QDLS QNTC
Standard part of IBM i Yes Yes Yes Yes Yes
Type of file Stream Stream Record 12 Stream Stream
File size limit T2=1 TB; T1=128 GB T2=1 TB; T1=128 GB Database file sizes 4 GB Varies 17
Access through IBM i file server Yes Yes Yes Yes Yes
Direct access through file server I/O processor 1 No No No No Yes
Comparative speed for open/close Medium 2 Medium 2 Low 2 Low 2 Medium 2
Case-sensitive name search No Yes No 4 No 5 No
Maximum length of each component in path name 255 characters 3 255 characters 3 10/6 characters 6 8/3 characters 7 255 characters 3
Maximum length of path name 8 16MB 16MB 55 – 66 characters4 82 characters 255 characters
Maximum length of extended attributes for an object 2GB 2GB Varies 9 32KB 0 18
Maximum levels of directory hierarchy within file system No limit 10 No limit 10 3 32 127
Maximum links per object 11 Varies 15 Varies 15 1 1 1
Supports symbolic links Yes Yes No No No
Object or file can have owner Yes Yes Yes Yes No
Supports integrated file system commands Yes Yes Yes Yes Yes
Supports integrated file system APIs Yes Yes Yes Yes Yes
Supports hierarchical file system (HFS) APIs No No No Yes No
Threadsafe 13 Yes Yes Yes No Yes
Supports object journaling Yes Yes Yes14 No No
Notes:
  1. The file server I/O processor is hardware used by the LAN Server.
  2. The speed applies when the file system is accessed through the IBM i file server.
  3. For certain CCSID values, the maximum length can be less than 255 characters.
  4. The QSYS.LIB file system has a maximum path name length of 55 characters. The independent ASP QSYS.LIB file system has a maximum path length of 66 characters.
  5. See Document library services file system (QDLS) for details.
  6. This value can be up to 10 characters for the object name and up to 6 characters for the object type.
  7. This value can be up to 8 characters for the name and 1 to 3 characters for the file type extension (if any).
  8. The values are based on the assumption that an absolute path name begins with / followed by the file system name (such as /QDLS...).
  9. The QSYS.LIB and independent ASP QSYS.LIB file systems support three predefined extended attributes: .SUBJECT, .CODEPAGE, and .TYPE. The maximum length is determined by the combined length of these three extended attributes.
  10. In practice, directory levels are limited by program and system space limits.
  11. An exception to this is a directory that can have only one link to another directory.
  12. The user spaces in QSYS.LIB and independent ASP QSYS.LIB file systems support stream file input and output.
  13. Integrated file system APIs are threadsafe when the operation is directed to an object that resides in a threadsafe file system. When these APIs are operating on objects in file systems that are not threadsafe when multiple threads are running in the job, the API will fail.
  14. QSYS.LIB and independent ASP QSYS.LIB file systems support journaling different object types than the "root" (/), UDFS, and QOpenSys file systems.
  15. *TYPE2 directories have a limit of one million links per object and a limit of 999 998 subdirectories. *TYPE1 directories have a limit of 32 767 links per object.
  16. Data in this column refers to both the QSYS.LIB file system and the independent ASP QSYS.LIB file system.
  17. This limit depends on the system being accessed.
  18. QNTC does not support extended attributes.

Abbreviations

  • T1 = *TYPE1 *STMF
  • T2 = *TYPE2 *STMF
  • B = bytes   KB = kilobytes   MB = megabytes   GB = gigabytes  TB = terabytes
Table 2. File system summary (Part 2 of 2)
Capability QOPT QFileSvr.400 UDFS NFS
Standard part of IBM i Yes Yes Yes Yes
Type of file Stream Stream Stream Stream
File size limit Varies16 Varies 3 T2 = 1 TB; T1=128 GB Varies 14
Access through IBM i file server Yes Yes Yes Yes
Direct access through the file server I/O processor 1 No No No No
Comparative speed for open/close Low Low 2 Medium 2 Medium 2
Case-sensitive name search No No 2 Yes 11 Varies 2
Maximum length of each component in path name Varies 4 Varies 2 255 characters 15 Varies 2
Maximum length of path name 5 294 characters No limit 2 16 MB No limit 2
Maximum length of extended attributes for an object 8 MB 0 6 2 GB 10 0 6
Maximum levels of directory hierarchy within file system No limit 7 No limit 2 No limit 7 No limit 2
Maximum links per object 8 1 1 Varies 13 Varies 2
Supports symbolic links No No Yes Yes 2
Object or file can have owner No No 9 Yes Yes 2
Supports integrated file system commands Yes Yes Yes Yes
Supports integrated file system APIs Yes Yes Yes Yes
Supports hierarchical file system (HFS) APIs Yes No No No 2
Threadsafe 12 Yes Yes Yes Yes
Supports object journaling No No Yes No
Notes:
  1. The file server I/O processor is hardware used by the LAN Server.
  2. This value depends on which remote file system is being accessed.
  3. When connected to a system earlier than V6R1, the file size limit is 2 GB-1. Otherwise, the file size limit depends on the file system being accessed.
  4. See Optical file system (QOPT) for details.
  5. The values are based on the assumption that an absolute path name that begins with / followed by the file system name.
  6. The QFileSvr.400 file system does not return extended attributes even if the file system being accessed supports extended attributes.
  7. In practice, directory levels are limited by program and system space limits.
  8. An exception to this is a directory that can have only one link to another directory.
  9. The file system being accessed might support object owners.
  10. The maximum length of extended attributes for the UDFS itself cannot exceed 40 bytes.
  11. Case sensitivity can be specified when a UDFS is created. If the *MIXED parameter is used when creating a UDFS, it will allow a case-sensitive search.
  12. Integrated file system APIs are threadsafe when they are accessed in a multithread capable process. The file system does not allow accesses to the file systems that are not threadsafe.
  13. *TYPE2 directories have a limit of one million links per object. *TYPE1 directories have a limit of 32 767 links per object.
  14. This limit depends on the system being accessed.
  15. For certain CCSID values, the maximum length can be less than 255 characters.
  16. 9,999,999,827,968 bytes when accessing through integrated file system. 4,294,705,152 bytes when accessing through hierarchical file system (HFS).

Abbreviations

  • T1 = *TYPE1 *STMF
  • T2 = *TYPE2 *STMF
  • B = bytes   KB = kilobytes   MB = megabytes   GB = gigabytes   TB = terabytes