Harbour File Size Limits


Harbour File Size Limits

  • Max record size: 2^16-1 = 65535 byts ( 64 MB )
  • Max number of recors : 2^32-1 = 4,294,967,295 ( 4 Bilion )
  • Max .dbf file size : 2^48 = 256 TB
  • Max DBT memo file size : 2 TB
  • Max FPT memo file size : 256 GB
  • Max SMT memo file size : 128 GB
  • Max NTX file size (standard) : 4GB
  • Max NTX file size (incresead ) : 4TB
  • Max CDX file size : 4GB


Source : Harbour\doc\xhb-diff.txt :

### NATIVE RDDs ###

In both compilers maximal file size for tables, memos and indexes is limited only by OS and file format structures. Neither Harbour nor xHarbour introduce own limits here.

The maximal file size for DBFs is limited by number of records 2^32-1 = 4294967295 and maximal record size: 2^16-1 = 65535 what gives nearly 2^48 = 256TB as maximal .dbf file size.

The maximal memo format size depends on used memo type: DBT, FPT or SMT and size of  memo block. It’s limited by maximal number of memo blocks = 2^32 and size of memo block so it’s 2^32*<size_of_memo_block>.

The default memo block size for DBT is 512 bytes, FPT – 64 bytes and for SMT 32 bytes. So for standard memo block sizes the maximum are:

DBT->2TB, FPT->256GB, SMT->128GB. The maximal memo block size in Harbour is 2^32 and minimal is 1 byte and it can be any value between 1 and 65536 and then any number of 64KB blocks. The last limitation is introduced as workaround for some wrongly implemented in other
languages memo drivers which were setting only 16 bits in 32bit field in memo header. Most of other languages has limit for memo block size at 2^15 and the block size has to be power of 2. Some of them also introduce minimal block size limits. If programmers plans to share data with programs compiled by such languages then he should check their documentation to not create memo files which cannot be accessed by them.

Maximal NTX file size for standard NTX files is 4GB and it’s limited by internal NTX structures. Enabling 64bit locking in [x]Harbour change slightly used NTX format and increase maximum NTX file size to 4TB.

The NTX format in [x]Harbour has also many other extensions like support for multitag indexes or using record number as hidden part of index key and many others which are unique to [x]Harbour. In practice all of CDX extensions are supported by NTX in [x]Harbour.

The NSX format in [x]Harbour is also limited by default to 4GB but like in NTX enabling 64bit locking extend it to 4TB. It also supports common to NTX and CDX set of features.

The CDX format is limited to 4GB and so far [x]Harbour does not support extended mode which can increase the size up to 2TB with standard page length and it can be bigger in all formats if we introduce support for bigger index pages. Of course all such extended formats are not binary compatible with original ones and so far can be used only by [x]Harbour RDDs though in ADS the .adi format is such extended CDX format so maybe in the future it will be possible to use .adi indexes in our CDX RDD.

Of course all of the above sizes can be reduced by operating system (OS) or file system (FS) limitations so it’s necessary to check what is supported by environment where [x]Harbour applications are executed. 

Format of xBase Files

xBase File Format Description

xBase File Types

xBase File  Types and Extensions

Ext. File Type  Introduced or used by
.$$$ temporary file  dBASE III
.$db temporary file  dBASE IV
.act FoxDoc Action Diagrams  FoxPro
.app application object file  dBASE Appl. Generator
.app generated application  FoxPro
.bak Backup file  dBASE
.bar horizontal bar menu object file  dBASE Appl. Generator
.bin Binary files  dBASE
.bch batch process object file  dBASE Appl. Generator
.cac executable when caching on/off  dBASE IV
.cat catalog  dBASE III, IV
.cdx compound index  FoxPro
.ch header file  Clipper
.cht interface file for ChartMaster  dBASE
.clp compiler script file (clip list)  Clipper
.cmd command  dBASE – Waffle
.cod template source file  dBASE Appl. Generator
.cpt encrypted memo file  dBASE
.crp encrypted database  dBASE IV
.ctl control file  dBASE IV – Aldus Setup
.cvt backup file for CONVERTed database file  dBASE IV
.db configuration  dBASE
.db$ temporary file  dBASE
.db2 database  dBASE II
.db3 database  dBASE III
.dbf database file  dBASE – FoxPro
.dbk database backup  dBASE IV
.dbo compiled program  dBASE IV
.dbt FoxBASE+ style memo  FoxPro
.dbt memo file for database w/same name  dBASE – Clipper
.def Definitions list  dBASE
.dif Data Interchange Format. For APPEND FROM, COPY  dBASE – VisiCal
.doc Documentation text file  dBASE Appl. Generator
.fil files list object file  dBASE Appl. Generator
.fky macro file  FoxPro
.fmo compiled format file  dBASE IV
.fmt format file  dBASE – FoxPro – Clipper
.fp configuration file  FoxPro
.fpc catalog  FoxPro
.fpt memo  FoxPro
.fr3 renamed dBASE III+ form file  dBASE IV
.frg uncompiled report file, code fragment file  dBASE IV
.frm report file  dBASE – Clipper
.fro compiled report file  dBASE IV
.frt report memo  FoxPro
.frx report  FoxPro
.fw2 Framework spreadsheet or database file  Framework – dBASE
.fxp compiled format  FoxPro
.gen compiled template  dBASE Appl. Generator
.idx index (many)  FoxPro
.ind include index  dBASE IV
.inx index  FoxBase
.key Key macro library  dBASE
.lbg label generator data  dBASE IV
.lbl label  dBASE – Clipper
.lbo compiled label  dBASE IV
.lbt label memo  FoxPro
.lbx label  FoxPro
.ld1 overlay file  dBASE
.log Transaction log file  dBASE
.mbk multiple index file backup  dBASE IV
.mdx multiple index file  dBASE IV
.mem memory variable save file  dBASE – FoxPro
.mnt menu memo  FoxPro
.mnx menu  FoxPro
.mpr generated program  FoxPro
.mpx compiled menu program  FoxPro
.ndx index file  dBASE
.npi source for DGEN.EXE interpreter  dBASE Appl. Generator
.ntx index file  Clipper
.pjt project memo  FoxPro
.pjx project  FoxPro
.plb library  FoxPro
.pll pre-linked library  Clipper
.plt pre-linked transfer file  Clipper
.pop pop-up menu object  dBASE Appl. Generator
.ppo pre-processor output  Clipper
.pr2 printer driver  dBASE IV
.pr3 PostScript printer driver  dBASE IV
.prf printer driver  dBASE IV
.prg program source file  dBASE – FoxPro – Clipper
.prs procedure  dBASE IV
.prt Print dump  dBASE
.prx compiled program  FoxPro
.qbe saved query (Query By Example)  dBASE IV – Quattro Pro
.qbo compiled query  dBASE IV
.qpr generated query program  FoxPro
.qpx compiled query program  FoxPro
.qry query  dBASE IV
.res dBASE resources  dBASE IV
.sc3 renamed dBASE III screen mask file  dBASE IV
.scr screen – screen snapshot  dBASE IV
.sct screen memo  FoxPro
.scx screen  FoxPro
.spr generated screen program  FoxPro
.spx compiled screen program  FoxPro
.str structure list object file  dBASE Appl. Generator
.t44 Temporary file for Sort or Index  dBASE IV
.tbk memo backup  dBASE IV – FoxPro
.tvf table view settings  dBASE
.upd update data  dBASE
.upo compiled update data  dBASE
.val values list object file  dBASE Appl. Generator
.vew view file  Clipper, Lotus Approach
.vue view  dBASE IV – FoxPro
.w44 temporary file for Sort or Index  dBASE
.wfm form object  dBASE Form Designer
.win window file  FoxPro – dBASE

Source :  http://www.clicketyclick.dk/databases/xbase/format/index.html


–          Such a list can’t be perfect. Some item may be obsolete / forgotten and something may not exist when this list compiled.

–          “Clipper” may not include all versions of Clipper.

–          Most of Clipper files are supported by Harbour.

Memo File Extension

#include "dbinfo.ch"
PROC Main()
* Test .prg for MemoFExtn() function

 SetMode( 25, 80 ) 
 ? "Memo File extension :", MemoFExtn() // NIL
 ? REPL( "-", 80 )

 cTfName := "MFInTst1"
 aStruct := { { "FLD1", "C", 10, 0 } }

 DBCREATE( cTfName, aStruct ) 
 USE ( cTfName )

 ? "Memo File extension :", ">" + MemoFExtn() + "<" // ><
 ? REPL( "-", 80 )

 cTfName := "MFInTst2"
 aStruct := { { "FLD1", "M", 10, 0 } }
 DBCREATE( cTfName, aStruct ) 
 USE ( cTfName )
 ? "Memo File extension :", MemoFExtn() // .dbt
 ? REPL( "-", 80 )

 cTfName := "MFInTst3"
 aStruct := { { "FLD1", "M", 10, 0 } }
 DBCREATE( cTfName, aStruct, "DBFFPT" ) 
 USE ( cTfName )
 ? "Memo File extension :", MemoFExtn() // .fpt
 ? REPL( "-", 80 )

 WAIT "EOF MemoFExtn.prg"

RETURN // MemoFExtn.Main()
Function MemoFExtn() -> Memo File Extension of current table

 Return : If current work area is empty : NIL 
 elseIf current table not include MEMO field : ""
 else .dbt / or .fpt depending RDD used in creation of current table.

 Required :
 #include "dbinfo.ch"
Aug 2012

FUNCTION MemoFExtn() // Memo file extension

 xRetVal := ""

RETURN xRetVal // MemoFExtn()