Limits of the current release

This file is aimed at HDF applications programmers and reflects upperbounds as of HDF 4.2r1.

Limits that are #define'd are fully capitalized. If the #define's are changed in order to meet the needs of an application, it is important to make sure that all other users, who would share the HDF library and the hdf files of the application, are aware of the changes.

If a limit has no #define, the size of the maximum storage allocated for that item is given; it would, generally, require a large amount of modification of the HDF library to change.

The limits are now kept in one single file hdf/src/hlimits.h.

hlimits.h

H-Level Limits

due to defines

   MAX_FILE      - files open at a single time            (32)
   MAX_ACC       - access records open at a single time   (256)
   MAX_PATH_LEN  - Maximum length of external filename(s) (1024)
   DEF_NDDS      - defalut # of DD's in a block           (16)
   MIN_NDDS      - smallest # of DD's you can set         (4)

due to number type size

   int16 total tags (fixed) 
   int32 max length and offset of an element in an HDF file (fixed)

Vgroup Limits

due to defines

   MAX_VFILE       - vset files open at a single time     (MAX_FILE)
   VGNAMELENMAX    - max length of a Vgroup name or class  (64 chars)
   MAXNVELT        - default max number of objects in Vgroup (64)
                     will grow dynamically.

due to number type size

   int16 elements in a Vgroup (fixed)

Vdata Limits

due to defines

   MAX_VFILE        - vset files open at a single time     (MAX_FILE)
   VSFIELDMAX       - fields in a Vdata                    (256) 
   FIELDNAMELENMAX  - characters in a single field name    (128 chars)
   MAX_ORDER        - max field order in a Vdata           (65535)
   MAX_FIELD_SIZE   - max size in a Vdata                  (65535)
   VSNAMELENMAX     - max length of a Vdata name or class  (64 chars)

due to number type size

   int16 max width in bytes of a Vdata record. (fixed)

Raster Images

due to number type size

   int32 width or height of a raster image. (fixed)

SD Limits

due to defines

   MAX_NC_OPEN      - files open at a single time           (MAX_FILE)
   MAX_NC_ATTRS     - attributes for a given object         (3000)
   MAX_NC_DIMS      - max dimensions per datset             (5000)
   MAX_NC_VARS      - max varibles per datset               (5000)
   MAX_VAR_DIMS     - max per variable dimensions           (32)
   MAX_NC_NAME      - maximum length of a name              (256)

due to number type size

   int32 maximum dimension length (fixed)

Other Conventions / Issues

Some utility programs (e.g. ncgen) expect dataset names to be composed of only alphanumeric, '-' and '_' characters.

- - Last modified:May 16th 2011