DISAM History, complete
The first DISAM was released in March of 1988.
This hisitory commences with Version 5.
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september 24th, 1995 - version 5.93 - first official release
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october 3rd, 1995 - version 5.94
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this version incorporates the initial release of variable length data
records, and two minor bug patches relating to data record locks and
natural order read/search.

---------------------------------------------------------------------
october 8th, 1995 - version 5.95
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this version includes an optional administration facility to keep
track of active isam file descriptors.

the administration facility allows the library to keep track of
duplicate opens on isam files and to share a single pair of system
file handles between duplicate instances of the same file.

ISMAXFILES and ISMAXLK are now redundant, and the associated tables
are now dynamically allocated, meaning that the number of open files
and the number of active record locks is now only limited by system
resources.

the initial beta version of the transaction processing module is
included. this version features an enhancement over the original
disam code in that it supports virtual open/close within transactions.
any attempt to close a file that is part of an active transaction
will be deferred until the transaction is complete. if you chose
to reopen the file within the same transaction, the virtual handling
system will just pass you back the same handle you were using before.
this, in theory, should help to correct the EMFILE errors inherent
in the original disam versions. refer to trans.ref for details.

the test/user.c executable has been enhanced slightly in that it can
now make system calls (sys) and run rudimentary scripts (run).

---------------------------------------------------------------------
october 16th, 1995 - version 5.97
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featuring a number of adjustments and enhancements to the variable
length option, and the implementation of a fairly rigorous storage
checking/statistics facility in ascheck.

the remainder of the changes cover basic adjustments for portability
and a degree of cleanup and optimisation in the remainder of the code.

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october 31st, 1995 - version 5.98
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initial beta - threadsafe and threadproof handling - see thread.ref
for more details.

implemented true support for duplicate opens within the same process.
record locking on duplicate handles is honoured, and locks will not
be lost when a duplicate handle is closed.

isrecover now returns appropriate error codes on failure.

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december 15th, 1995 - version 5.99
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essentially a collection of adjustments based on beta test reports.
added isprecious() and islockcheck() options to the wrapper code.

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january 2nd, 1996 - version 6.0
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the updates in this version consist of the inclusion of the isCluster
and isAudit calls, documented in base.ref and audit.ref respectively.

---------------------------------------------------------------------
january 28th, 1996 - version 6.1
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the transaction processing module has been upgraded to comply with
the current cisam standard, and includes full support for variable
length records. disk i/o has been improved (at the expense of an
extra chunk of memory) and the lock time on the file log reduced.

added ISDUPLOCKS option to the configuration options to permit
cisam (non xopen) functionality with regard to duplicate opens
in the same process - see entry for version 5.98 for more detail.
please note that ISDUPLOCKS should not be set to zero when porting
do DOS, Windows, OS/2 or non ELF versions of Linux. if this is a
problem to you, please contact Byte Designs.

the flag structure in the index header that denotes ISMASKED files
has been changed. this means that masked files built before this
release are no longer compatible. the fixflags utility in the util
directory will patch existing files to comply with the new method.

added isindex, ispop, iscopy and isclone calls - see upgrade.ref
for further details.

the ascheck utility now includes a -B option to allow specific indexes
to be rebuilt without disturbing the remainder. see ascheck.ref for
more details.

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february 5th, 1996 - version 6.2
---------------------------------------------------------------------

isClose now returns a boolean TRUE or FALSE rather than the original
NULL pointer. this change is specific to the base library and does
affect the standard interface.

base and wrapper function prototypes are now C++ compatible.

added isseekey() to the wrapper library.

ascheck now does index/data mismatch checking - slower but better.

aslist in the util directory is an incomplete but fully functional
means of listing the contents of an isam index file.

added isPush and isPop to the base library.

added threadsafe isvbuild to the wrapper to allow building variable
length files without the use of the global isreclen variable.

added isWrCurr and iswrcurr to the base and wrap libraries.

added isfilter (wrapper only) and islkcall (inhouse only)

pure index files - see pure.ref

transparent file links - see link.ref

stubs for isstat variables - see status.ref

added ISRDONLY mode in isopen for handling read only files.

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february 14th, 1996 - version 6.4
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null key masking - see nullkeys.ref

custom key extensions - custkeys.ref

RLE compression option for variable length - ISVARIABLE in install.ref

renamed isLockMode and islockmode to isSetMode and issetmode.

implemented ISSYNCWR mode in open and build - see base.ref

upgraded isprecious logic to complete implementation

adjusted isGoto to not return an error if file not open for reading.

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version 6.5 was an interim release, changes from 6.4 covered below.
---------------------------------------------------------------------

---------------------------------------------------------------------
february 14th, 1996 - version 6.6
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threadsafe transaction processing module - beta only - see
trans.ref for details.

added ISVARCMP mode on isbuild to allow runtime compression
flagging on variable length files, adjusted variable length
compression handling, and added ISNOCARE option to isOpen to
allow easier handling of varlen files - see varlen.ref for
details.

reworked threadsafe duplicate open handling.

added EINTR handling to lockmode 2 for threadsafe, and allowed
multiple lock fail codes to be specified in isport.h

stchar arguments were reversed, and the float machine independant
routines now have float arguments rather than double.

open and build now allow the lock mode to default to ISMANULOCK
if not specified.

adjusted isStart behaviour to match cisam standards.

cleaned up a number of compiler warnings.


---------------------------------------------------------------------
march 22nd, 1996 - version 6.7
---------------------------------------------------------------------

allow varlen compression to be specified on a per file basis,
see varlen.ref

implemented ISNOCARE open mode to make it easier to open unknown
(varlen or fixlen) files. also modified isgetmode to get all
open mode bits rather than masking out only the lock mode, and
adjusted issetmode to accept an unmasked mode value without
complaint. see varlen.ref

added common dictionary access - see wrap.ref, should be of
value to those converting from old disam.

error code offset value define - see install.ref

added varlen and varcmp mention in ascheck.

display contents of known key types in aslist.

user info pad in index headers - see info.ref

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april 10th, 1996 - version 6.8
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adjusted ISDUPLOCKS 1 mode to disallow erase/rename on files already
open in the current process - DUPLOCKS 0 retains original behaviour,
but be warned that a sequence of open, erase, write, close will result
in data loss - see install.ref and caveat.ref for details.

added isdi_kdsc() to the wrapper library - see wrap.ref

library expiration date option - see expire.ref

---------------------------------------------------------------------
may 3rd, 1996 - version 6.9
---------------------------------------------------------------------

added NPARTS define for cisam/xopen compatibility.

completed ISDATAVOID conditioning in the wrapper interface.

added missing TNULL key compression option.

corrected STRINGTYPE key loading bug.

added missing key description validity checks.

no longer legal to erase the last remaining index in a file.

overflow on opening files with too many indexes no longer fatal.

isdelcurr will now fail after isstart first/last.

adjusted error return code in isrewcurr and isdelcurr on empty file.

corrected dislocation problems caused by use of is_recnum().

revised error return conditioning in isread and isstart to ensure
appropriate error returns under various conditions.

isread ISNEXT now returns current after ALL isstart operations
except isstart ISNEXT.

corrected non-portable bug when selecting descending order indexes.

adjusted isgoto to handle natural order index properly.

isolated natural order current.

null flag in stfltnull and stdblnull should not have been a pointer.

aspack was not handling null primary indexes properly.

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august 18th, 1996 - version 6.10
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much pruning and transplanting..

the source is now distributed in two flavours - standard unix format,
and a dos/win/os2 version. both are generated from the same meta
source but contain unique platform extensions.

base/ismemory.c and wrap/stdmif.c must be added to make/project.

now only four headers. isconfig.h is common to all, isbase.h and
iswrap.h as before, iscustom.h is optional.

isport.h is gone, as is ISPLATFORM. BSD extensions and threadsafe
configuration are now in isconfig.h

added isLockCheck to the base interface, parallel to islockcheck
in the wrapper.

the base now has it's own mif calls - ldInt, stDblNull, etc, and
these have been wrapped for access from the standard interface.

added isErrno, isErrio, isRecNum, isRecLen, isSetRec, isSetLen
calls to base.

additional support for DLL compilation included, see dynamic.ref
for more details.

additional support for microsoft windows added, see windows.ref
for more details.

misc/dbmemory.c is a debugging replacement for ismemory.c, see
same for comments and usage.

added ISLOCKING 3 for dos based systems and support for 'lowest
common denominator' NFS based configurations.

the built in check call prototypes, codes and structures are now
included in both the base and wrapper headers, and ischeck.h is
no longer provided or required.

entry function prototyping has been revised to provide more
flexible support for building dynamic link libraries.

the general lock handling scheme has been revised somewhat to
cover requirements arising from the ISLOCKING 3 option.

corrected a relatively obscure memory under-run bug in the tree
pruning module.

added isLastRec(), isGetLastRec(), isSetLastRec() to the base,
islastrec(), isgetlastrec(), issetlastrec() to the wrapper. must
add base/islast.c and wrap/stdlast.c respectively to make/project
to use. undocumented (as yet)

added base library file descriptor sanity checks

corrected invalid eof on read next after adding records to an
empty file.

pure indexes not following isfirst/isnext rules after delete
and erase corrected.

transaction processing - commit/rollback was failing when no
updates made within transaction.

isStart/isstart should not allow the user to set keylength greater
than the length of the selected key.

isCopy/iscopy was reporting a bogus error on success.

build and addindex were being a bit too fussy about the contents
of a null key descriptor.

isindexinfo and related were not counting null primaries.

lock handling not releasing internal record lock state flags under
some situations.

------------------------------------------------------------------------------
october 16th, 1996 - Version 6.11 - James Knight bids his official farewell
------------------------------------------------------------------------------

Byte Designs assumes ownership of Disam96 - changes to copyright/banners

ascheck, aspack and aslist references changed to dcheck, dpack and dlist
respectively

------------------------------------------------------------------------------
sept 1st, 1997 - Version 6.12
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dec modules standardize to fit disam96 function prototyping

isclone ensures null primary is cloned

compnext now returns FALSE if no current record

isopen reuses system fds on failure

dpack copies unique ids on rebuild

dcheck added -q quiet mode option

iserrno initialization on successful return

int64 support for maintenance of large files, ISHUGE 1 in isconfig.h

cisam version 7.1 locking concurrency added, C7LOCKING 1 in isconfig.h

rewnxt/RewNxt now correctly returns EENDFILE rather than looping on last
record

extensive transaction processing rewrites

cisam 7.1 no-wait on open and automatic record locks, C7NOWAIT 1 in isconfig.h

cisam isstat cobol variables implemented

-------------------------------------------------------------------------------
may 1st, 1999 - Version 6.13 - Client / Server
-------------------------------------------------------------------------------

client/server capability - see client.ref

file mirroring capibilty - see mirror.ref

-------------------------------------------------------------------------------
january 15th, 2000
-------------------------------------------------------------------------------

addtional c-isam behaviour implementations - C7NOWAIT set to 1
ISSKIPLOCK and no skip on locked records

fix to ensure deletions of compressed index values don't cause uncompression
of previous index values to bump past end of node - caused 105 EBADFILE errors

-------------------------------------------------------------------------------
may 1st, 2000
-------------------------------------------------------------------------------
c-isam version 7.2x locking concurrency support

isconfig.h - C7LOCKING setting should be set to 2

-------------------------------------------------------------------------------
july 5th, 2000
-------------------------------------------------------------------------------
added the utility - dsplit - allows a large file to be split into two smaller
files.

------------------------------------------------------------------------------
january 16th, 2001
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added libinfo structure in association with new subroutines isLibInfo()
and islibinfo(). isLibInfo()/islibinfo() when called with an empty libinfo
pointer, will load the libinfo structure with the expiration date, if set,
the library compilation date and the number of clients if set.

added asplog flag to ensure that socket error reporting within the client
code, is logged to a file rather than displayed. new functions, AspGet()
and AspSet( int flag ) in the base library code and, aspget() and
aspset( int flag ), will set and report the current value of asplog.

several refinements to the client/server code..extensive log reporting.

added dstat utility that reports library statistics, see dstats.ref for
more information.

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may 1st, 2001
---------------------------------------------------------------------------
added auto repair for index/data corruptions that may occur if a process
is killed or if a system failure occurs. see repair.ref and ISREPAIR
setting in isconfig.h

----------------------------------------------------------------------------
september, 2001
----------------------------------------------------------------------------
added ISCISAM 2 option - same as ISCISAM 1, ie. mimic C-ISAM behaviours, but
with the addition of ENOCURR on isread/ISEQUAL failure.

duplicate count logic - rev.2 - isgrow.c effected.

added check for ISWAIT on AUTOLOCK open with ISCISAM > 0 or ISNOWAIT 1

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november, 2001
----------------------------------------------------------------------------
isIndexInfo/isindexinfo - EBADARG(102) when file opened with other than
ISINOUT
versions effected: 6.12 unix and MS, 6.13CS unix and MS - isinfo.c

isupdate.c, isdelete.c - increased allocated size of oldpad buffer
general reorganization of rewrite() and delete() routines for better
efficency.c
versions effected: 6.12 unix and MS, 6.13CS unix and MS

added more functionality to ISAUDIT - additional options 2 through 7 see
audit.ref
tune which operations are audited, see audit.ref for options
versions effected: 6.12 unix and MS, 6.13CS unix and MS
isconfig.h, isdelete.c, isupdate.c and iswrite.c

----------------------------------------------------------------------------
january, 2002
----------------------------------------------------------------------------
addition of remote system functions - eg. fread, fwrite etc.

----------------------------------------------------------------------------
may, 2002
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ISKCOMP - compile time flag - isconfig.h - see compkey.ref for details

isprune.c replacement to correct index count and fatal errors encountered
during continuous rewrite cycles where the key values are effected

----------------------------------------------------------------------------
aug, 2002
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isadmin.c - correction to reference ADM(id)->isam->openmode should
read ADM(did)->isam->openmode

isrepair.c - modifications to correct repaired writes

isadmin.c, iserase.c - iserase() failure caused admin table corruption

isdelete.c - drop record lock prior to adding record number to free
list

----------------------------------------------------------------------------
sep, 2002
----------------------------------------------------------------------------
isprune.c - corrected bug that caused index mismatch errors under
certain conditions

ISLOCKING 3 on unix platforms would incorrectly initialize isam->iserrno
to 0, overwriting a valid error value

isadmin.c - dup struct pointer not freed on open failure, corrected

----------------------------------------------------------------------------
nov, 2002
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isprune.c - dupnum calculation on insertion into new root corrected

----------------------------------------------------------------------------
jan, 2003
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isbuild.c, isopen.c, isopen.c and isbase.h - added CISAM compatible
ISSEMILOCK. see #define SEMILOCK in isconfig.h

----------------------------------------------------------------------------
feb, 2003
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issystem.c, isconfig.h, iswrap.h, isbase.h, stdwrap.c and stdwrap.h
added ISEXTENDED compile time option to allow for extended lock
reporting when locks are blocked by other processes. see read/extended.ref

----------------------------------------------------------------------------
mar, 2003
----------------------------------------------------------------------------
isIndexInfo/isindexinfo - EBADARG(102) when file opened with other than
ISINOUT
versions effected: 6.12 unix and MS, 6.13CS unix and MS - isinfo.c

----------------------------------------------------------------------------
may, 2003
----------------------------------------------------------------------------
ISCISAM > 0 check for natural order - isread.c
ISCISAM > 0 allow ISOUTPUT record locking, ie. isLock()/islock()

----------------------------------------------------------------------------
aug, 2003
----------------------------------------------------------------------------
isconfig.h - D3XAUTOLOCK set to 1 in isconfig.h prior to compiling the
library will enable older D-ISAM v3.x behaviour releasing record locks
on subsequent read, update or delete

ischeck.c - additional check for last datfree corruption

----------------------------------------------------------------------------
jan, 2004
----------------------------------------------------------------------------
isgrow.c - change to satisfy C-ISAM bcheck higher level node ordering
problem did not effect the integrity of the isam file or
Disam96's ability to maintain the file.

----------------------------------------------------------------------------
feb, 2004
----------------------------------------------------------------------------
isread.c - change to ensure partial key searches are C-ISAM compatible
when ISCISAM set to non-zero
Note difference between C-ISAM and Disam96 in the following
scenario.
Set key compare length to partial key length via isstart()
Given 3 records with key values of 1110, 1120 and 1130
setting compare length to 1 will result in
isread/ISFIRST - first record with key 1110 is returned
isread/ISGREAT - iserrno 111 - ENOREC - Disam96
Since only the first byte of the key is compared and none
are greater than the value of 1. With C-ISAM the isread/ISGREAT
will return the key 1120 record, which means the isstart
setting of partial key length compare to 1 doesn't have any
effect.

----------------------------------------------------------------------------
mar, 2004
----------------------------------------------------------------------------
isgrow.c - previous change to satisfy C-ISAM bcheck not quite correct
for uncompressed keys - refined/corrected. compressed
key logic correct.

----------------------------------------------------------------------------
jul, 2004
----------------------------------------------------------------------------
isadmin.c - rewrite of dup mutex handling on failure. Mutexes were
being unlocked rather than destroyed on function failure, isAdmFail

isentry.c - reversal of isAdmFail() and isDropLock() in isFail().
mutexes were being destroyed before being unlocked.
This problem first appeared on Itanium where stricter control
of mutexes exist. All platforms effected.

isread.c - ISCISAM 2 specific - ensure check for ISPATH->recnum is only
done when reading by index and not for natural or record number
order reads.

----------------------------------------------------------------------------
sep, 2004
----------------------------------------------------------------------------
iserase.c - Correction of bug that allowed erase/rename of locked file.

----------------------------------------------------------------------------
nov, 2004
----------------------------------------------------------------------------
isread.c - change in ISCISAM 2 ENOCURR check

----------------------------------------------------------------------------
aug, 2005
----------------------------------------------------------------------------
isadmin.c, stdextra.c, isbase.h - changes to correct isAdmFail master lock
end rather than drop. addition of new function isThreadedDone()/
isthreadeddone() to drop master lock. application code should call
isthreadeddone() prior to the application exiting..closing to isthreaded()
call.

----------------------------------------------------------------------------
oct, 2005
----------------------------------------------------------------------------
isaudit.c - changes to correct behaviour to conform to C-ISAM/X-OPEN,
original behaviour can be reinstated by defining D96ORIG in isaudit.c

----------------------------------------------------------------------------
feb, 2006
----------------------------------------------------------------------------
islock.c - correction to only set bit in lkstate for lock all and not
record

----------------------------------------------------------------------------
sep, 2006
----------------------------------------------------------------------------
isprune.c - reset node->recnum after compressed key delete

----------------------------------------------------------------------------
nov, 2007
----------------------------------------------------------------------------
isbase.h,iswrap.h,isread.c - isStart() added C-ISAM ISKEEPLOCK functionality
isopen.c - ensure isAdmClose if isopen fails while logging in progress

isvarlen.c - allocation of isam->hashtab changed from hardcoded 4 to
sizeof( long * ), to ensure proper support of platforms where
long is > 4 bytes, namely native 64bit environments.

----------------------------------------------------------------------------
jan, 2008
----------------------------------------------------------------------------
istrans.c - replaced missing call to isVLread in log_vdel routine to ensure
isrollback() reinserts variable length portion of deleted record.

----------------------------------------------------------------------------
jan, 2009 - offical release of DISAM v7.0 new to this release
----------------------------------------------------------------------------
isopen.c, isbuild.c, isvarlen.c, isvarlen.h and isconfig.h - changes to
variable length idx file format to allow for > 16777216 record limit when
storing record numbers in 3 char bytes for varinfo and continuation node
pointers. isconfig.h setting ISOLDVARLEN 1 or any non 0 ISCISAM setting
will maintain old disam/c-isam variable length file format compatibility.
ISCISAM 0 and ISOLDVARLEN 0 ensures new format. new format requires that
dvlrebld( see dvlrebld.ref ) be run on existing variable length files.

stdextra.c - schema/record layout support - new wrap functions
load schema from isamfile to path/filename
ISD1 int ISD2 isldschema( int isfd, char *path )
dump schema from isamfile to stdout
ISD1 int ISD2 isdpschema( int isfd )
store schema from loadfile to isamfile
ISD1 int ISD2 isstschema( int isfd, char *loadfile )
remove schema from isamfile
ISD1 int ISD2 isrmschema( int isfd )

isschema.c - schema record layout support - new base functions
load schema from isamfile to path/filename
ISD1 int ISD2 isLdSchema( IsFile *isam, char *path )
dump schema from isamfile to stdout
ISD1 int ISD2 isDpSchema( isFile *isam )
store schema from loadfile to isamfile
ISD1 int ISD2 isStSchema( IsFile *isam, char *loadfile )
remove schema from isamfile
ISD1 int ISD2 isRmSchema( IsFile *isam )
* see read/schema.ref for function details and schema/ReadMe for sample programs

dreport.c - new schema related isam data reporting utility.

record number limit changed from LONG_MAX to ULONG_MAX value

client/server capabilities incorporated into standard DISAM. for a limited single client server program please contact ByteDesigns.
----------------------------------------------------------

DISAM History, Version 7
jan, 2009 - offical release of DISAM v7.0 new to this release
----------------------------------------------------------------------------
isopen.c, isbuild.c, isvarlen.c, isvarlen.h and isconfig.h - changes to
variable length idx file format to allow for > 16777216 record limit when
storing record numbers in 3 char bytes for varinfo and continuation node
pointers. isconfig.h setting ISOLDVARLEN 1 or any non 0 ISCISAM setting
will maintain old disam/c-isam variable length file format compatibility.
ISCISAM 0 and ISOLDVARLEN 0 ensures new format. new format requires that
dvlrebld( see dvlrebld.ref ) be run on existing variable length files.

stdextra.c - schema/record layout support - new wrap functions
load schema from isamfile to path/filename
ISD1 int ISD2 isldschema( int isfd, char *path )
dump schema from isamfile to stdout
ISD1 int ISD2 isdpschema( int isfd )
store schema from loadfile to isamfile
ISD1 int ISD2 isstschema( int isfd, char *loadfile )
remove schema from isamfile
ISD1 int ISD2 isrmschema( int isfd )

isschema.c - schema record layout support - new base functions
load schema from isamfile to path/filename
ISD1 int ISD2 isLdSchema( IsFile *isam, char *path )
dump schema from isamfile to stdout
ISD1 int ISD2 isDpSchema( isFile *isam )
store schema from loadfile to isamfile
ISD1 int ISD2 isStSchema( IsFile *isam, char *loadfile )
remove schema from isamfile
ISD1 int ISD2 isRmSchema( IsFile *isam )
* see read/schema.ref for function details and schema/ReadMe for sample programs

dreport.c - new schema related isam data reporting utility.

record number limit changed from LONG_MAX to ULONG_MAX value

client/server capabilities incorporated into standard DISAM. for a free limited single client server program please contact ByteDesigns.
-----------------------------------------------------------------------------

This problem may be occurring in other Linux type distributions as well.
If you're running a multi-threaded DISAM program on Linux Ubuntu, with multiple processors and are seeing what appears to be a deadlock scenario, try switching to the latest Ubuntu 9.1. We have been able to confirm that some kernel versions that run NPTL threads on multi-processor systems run into what appears to be a bug in the kernel or NPTL threads library, specifically a futex_lock failure that kills the thread leaving other waiting threads in a permanent wait condition. To date we have not been able to duplicate this bug with the latest version of Ubuntu 9.1, specifically kernel 2.6.31-14 server. NPTL version 2.10.1.

Is D-ISAM compatible with Informix C-ISAM?
D-ISAM 3.x, DISAM96 and DISAM7 are all file compatible with C-ISAM. D-ISAM 3.x, DISAM96/DISAM7 will run concurrent locking with C-ISAM Version 4.1 executables. DISAM96 and DISAM7 allows for configuration settings that will enable concurrent locking with C-ISAM 5.1 and greater. ( Currently this applies to unix fcntl() environments only ) This is only of importance if you are planning to run C-ISAM executables against D-ISAM/DISAM96/DISAM7 executables. The D-ISAM 3.x calls and DISAM96/DISAM7 wrap calls are fully compatible with the standard C-ISAM isam function calls.

I'm sure I have compiled the library properly, and I'm sure I have compiled and linked my application properly but nothing seems to work correctly.
A. Ensure your including the correct header information, if compiling or converting from C-ISAM you'll need to change references from isam.h to disam.h ( versions 3.x ) or iswrap.h ( DISAM96/DISAM7 )..or simply create a dummy isam.h that only includes #include or .

B. Disam requires that that library be compiled with signed char types as the default. Ensure the compiler is defaulting to signed char types on compile or set the compiler flag that generates signed char types by default.

I'm sure I have compiled the library properly, and I am sure I have the right linker commands, but I keep getting unresolved references to the base ( isXxxx() ) library functions.
DISAM96/DISAM7 specific - If you're linking wrap ( isxxxx() ) calls then it is possible your linker resolves references canonically - in a single pass through the listed libraries. Linker objects should be listed in order of precedence - object module(s), wrap lib, base lib.

What's involved in converting from C-ISAM or D-ISAM 3.x to DISAM96/DISAM7?
If converting from C-ISAM to D-ISAM 3.x the only change you will need to make is to create an isam.h that only includes . Compile the D-ISAM 3.x library and recompile your application code and link to the D-ISAM library.

If converting from C-ISAM or D-ISAM 3.x to DISAM96 or DISAM7, you will need to ensure that references to isam.h or disam.h are replaced with iswrap.h. DISAM96 and DISAM7 no longer use the isfdmap structure that is internal to D-ISAM 3.x, DISAM96 and DISAM7 provide analogs for some of the more common values via common dictionary access routines.

512 index node size, dup width of 2 bytes and assuming no index compression: 100 byte key value, with 2 keys

one 512 byte node would be allocated for every 4 - 100 byte index values ( there is extra space per node 2 bytes for the #bytes used in node  as well as 4 bytes per value for record# and 2 bytes per value for dup# ) so 10 records of 100 bytes would mean 4 index values per node = 3 nodes * 512bytes * # file indexes

key length - 100 bytes + 4 bytes - record# + 2 bytes - dup# ---------- 106 bytes per index value

512 - index header record + 3 * 512 - 10 index values for key 1  + 3 * 512 - 10 index values for key 2 --------- 3584 bytes for index values + header record for .idx file

and 101 per data record * 10 records = 1010 bytes for the .dat file.

1024 index block size and 4 byte dup width ( now standard ) 9 index values in 1 node, another node for the 10th value

1024 - index header record + + 2 * 1024 - 10 index values for key 1 + 2 * 1024 - 10 index values for key 2 --------- 5120 bytes bytes for .idx

Once a node is full, that node is split into to 2 nodes and another level node is created. This forms the index chain. The first node is the level 0 node and level 0 nodes point directly to data records. Higher level nodes point to the index record of the lower level node in the index chain.