CREATE-FILE
The CREATE-FILE command enables the user to create a new file for use within the jBASE system.
CREATE-FILE {-L} {DICT|DATA} FileName{,Section} {HASHMETHOD=nnn}
{TYPE=tname} {PERM=nnn} {LOG=YES|NO} {TRANS=YES|NO}
{BACKUP=YES|NO} {SECURE=YES|NO} {NETWORK=YES|NO}
{NumBuckets, BucketMult, SecSize} {NumBuckets, BucketMult, SecSize}
Where:
-L
This option prevents any updates to this file from being recorded in the
Transaction Journal entries. It does the same thing as LOG=NO.
DICT
This is an optional keyword to specify dictionary section creation only.
DATA
This is an optional keyword to specify data section creation only.
FileName
This is the name to be used for the created file. The name can include absolute
or relative path information.
Section
This is the name to be used for the new data section to be created.
HASHMETHOD
The hash method defines how the records are allocated into the file buckets or groups. The
hash methods can make slight differences to performance dependent upon the values of the
record keys, however the methods can also improve the performance of the Account Restore
dependent upon source of file. The numeric parameter can be one of the following:
1 - Uniform hash algorithm
2 - General hashing algorithm
3 - Pick/Reality hash emulation
4 - Sequoia hash emulation
5 - jBASE hashing (provides the best spread for item-ids regardless of whether
item-ids are alpha, numeric or a combination)
TYPE
The tname parameter is used to specify the type of file to be created.
The following file types are provided as standard.
HASH3 or j3
The HASH3 file type is portable across platforms and
is network friendly in that if a network connection is disconnected during the update
procedure then file integrity can still be guaranteed. The HASH3 file type does not use
the jRLA or jDLS locking even when enabled but uses the default system locking capability, thus
allowing record or item locking with networked applications. The default bucket size of a
HASH3 file is 1024 bytes. See
JEDI_SECURE_LEVEL for configurable levels of data flushing.
HASH4 or j4
The HASH4 file type uses memory mapping when
available, otherwise defaults to reads and writes and is portable across platforms. The HASH4 file type will use jRLA
or jDLS locking when
enabled but can also be configured to use the default system locking method for networking. The default bucket size of a HASH4 file is 4096 bytes.
j4 files use 'INT32' for any offsets, in order to provide compatibility with
previous versions of jBASE. As such, j4 files should only be used where the file
size will not exceed 2Gb.
jPLUS or JP (jBASE 4.1 and 5.2)
jPLUS files provide large file support on 64 bit UNIX and Windows platforms,
such that Hash files can extend beyond the normal 2GB operating system limit. In
addition, jPLUS files provide configurable levels of data flushing (see
JEDI_SECURE_LEVEL) to ensure
file integrity in the case of a system failure. Some Operating Systems require
large file support to be enabled when the file system is created. Refer to your
System Administration Guide for your specific platform.
JR (jBASE 5.2)
JR files are a new file type introduced in jBASE 5.2. They are highly resistant
to corruption and also have the ability to auto-resize themselves as the file
size increases. Further information on JR files may be found
here.
The UD file type specifies NT or UNIX directories and NT or UNIX files are to be used to
represent file and records respectively.
TJLOG
Creates a stub file in the current directory that points to the current transaction log
set. An additional parameter, SET can be used to specify the log set. For more information
see jlogdup.
DISTRIB
Creates a stub file in the current directory that references a distributed file. See
distributed files for further information.
PERM
The PERM parameters are used to set the permissions of the file as per the chmod command.
i.e. an octal number nnn. By default the value is 666 and will be masked by the current
umask setting.
LOG=YES|NO
The LOG parameters set or clear the flag which allows the file to be included or excluded
when utilizing the item or transaction logging mechanism, if licensed on your system. The value is set to YES by default.
TRANS=YES|NO
The TRANS parameters set or clear the flag which allows the file to be included or
excluded from within any transaction boundaries defined by an executing program. The value is set to YES by default.
BACKUP=YES|NO
The BACKUP parameters set or clear the flag which allows the file to be included
automatically by the jBASE jbackup utility. The value is set to YES by default.
NETWORK=YES|NO
The NETWORK parameters disable or enable the file for use over a network. Only
applicable to HASH4 and HASH5 file types. The value is set to AUTO by default to
use jDLS when enabled.
SECURE=YES|NO
The SECURE parameters disable or enable secure file updates. Only applicable to HASH3
and jPLUS file types. The value is set to NO by default.
NumBuckets
NumBuckets and BucketMult combine to size a hash file. NumBuckets specifies the number of hashing buckets to allocate to the file.
BucketMult
BucketMult defines the size of each bucket in multiples of block size, usually
4k, and defaults to 1 if omitted. The
first instance of this construct specifies the size of the dictionary section of the file
while the second instance specifies the size of the data section of the file.
SecSize
SecSize can be used to change the maximum record size that will be stored within the
primary bucket. SecSize is specified as a multiple of the primary bucket size. If a record
is to be stored that exceeds this size, it is allocated new space within the file and a
pointer to the record is installed in its hash bucket. If the file is to contain many
unevenly sized records, the most efficient way of creating the file is to specify a
secondary bucket size of 0. This will cause all records to be stored as pointers to their physical location on disk.
NOTES
A hashed file should be created with enough space to hold the expected number
of records. Given the number of records and the average size of each record the
number of buckets can be calculated. The default bucket size of 4k should only be
changed if the average record size is much greater than this value.
The value of NumBuckets must be an odd number and usually works best if it is a prime
number. CREATE-FILE will change the value of NumBuckets if you supply an even value.
The CREATE-FILE command will always create the file in the current working directory
unless a full explicit path is specified;
the environment variable JEDIFILEPATH has no with meaning in the context of file creation.
Beware of creating a file and then immediately deleting it using the DELETE-FILE command. The DELETE-FILE command will respect
the JEDIFILEPATH variable and if it finds a file of
the same name in a directory earlier in the path than the current working directory it
will delete that file. For this reason it is best to define the JEDIFILEPATH variable as
"." (the current working directory).
The file options can be modified after the file has been created using the jchmod utility.
On Windows there are certain restricted filenames. See the Microsoft
Knowledgebase article
here.
EXAMPLES
CREATE-FILE File1 1 37
File File1]D created, type = j4
File File1 created, type = j4
Creates a dictionary file modulo 1, (1 bucket of 4096 bytes), and a data file modulo 37,
(37 buckets, primary size 151552, (37*4096)). The actual file size will be slightly larger to accommodate internal bucket pointers.
CREATE-FILE File2 1 37,3
File File2]D created, type = j4
File File2 created, type = j4
Creates a dictionary file modulo 1, ( 1 bucket of 4096), and a data file modulo 37 with
separation of 3, ( 37 buckets at 3 times page size, primary size 454656, (37*(3*4096))).
The actual file size will be slightly larger to accommodate internal bucket pointers.
CREATE-FILE DICT File3 TYPE=HASH3 SECURE=YES 23
Creates a dictionary-only file of type j3 modulo 23, with secure updates enabled.
The JEDI_SECURE_LEVEL environment
variable can be used to set different levels of data flushing.
CREATE-FILE DATA File4 1000003 TYPE=JP SECURE=YES
Creates a large date-only file of type jPLUS with a modulo of 1000003, with secure updates enabled.
A file of this size is only supported on 64 bit platforms.
The JEDI_SECURE_LEVEL environment
variable can be used to set different levels of data flushing.
CREATE-FILE File5 NETWORK=YES 101
Creates a dictionary and data section file of type j4, which only uses network locks.
CREATE-FILE H:\Payables\File6 3 431
Creates a dictionary and data section of type j4 on network drive H, directory Payables.
Files
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