The structure description file is a text file you prepare that defines the database structure. It contains all of the information required by the PROSTRCT CREATE utility to create a database control area and the database extents.

Use a text editor to create the structure description file. The name you give to the structure description file is usually the name of the database you define, with a .st extension.

The structure description file contains one or more lines of text that provide information about each storage area of the database. Each line of text is composed of tokens, which are text strings made up of alphanumeric characters that describe the following characteristics:

  • The storage area type
  • The area name
  • The area number
  • Optionally, the records per block
  • Optionally, the number of blocks per cluster (for Type II data storage areas)
  • The extent pathname
  • The extent type
  • The extent size

The following grammar rules how the 8 tokens are combined to form line in a structure description file: 

line     = comment | CR | type path [sizeinfo]

comment  = * | : | #

CR       = blank line

type     = a | b | d | t [areainfo]     
   areainfo = "areaname"[:areanum][,recsPerBlock][;blksPerCluster]           
      areaname       = string
      areanum        = numeric value
      recsPerBlock   = numeric value
      blksPerCluster = 1 | 8 | 64 | 512

path     = string

sizeinfo = extentType size
     extentType     = f | v | e | ev | x | xv
     size           = numeric value > 32
Note: You can comment a .st file and use blank lines. Precede comments with a pound sign (#), colon (:), or asterisk (*).

The table below explains the value of each of the 8 tokens in a structure description file.

Table 1. ST file tokens
Token Description
type Indicates the type of storage area. Possible values are:
  • a — After-image area
  • b — Before-image area
  • d — Schema and application data areas
  • t — Transaction log area
areaname Name of the storage area.
areanum Number of the storage area.
Note: If you do not include the area number token, PROSTRCT will assign the area numbers for you. However, if you choose to specify a number for one area in your .st, you must specify area numbers for all the areas or PROSTRCT will return an error.
recsPerBlock Number of database records in each database block. Valid values are 1, 2, 4, 8, 16, 32, 64, 128, and 256.
Note:
  • This token only applies to areas 7 through 32,000.
  • For the schema area, records per block is fixed at 32 for 1K, 2K, and 4K database block sizes, The records per block is 64 for an 8K database block size.
blcksPerCluster Number of database blocks in each cluster. Possible values are: 1, 8, 64, or 512.
Note:
  • If you leave this value blank, or specify 1, the data area will be Type I. All other values are valid for Type II data areas only.
  • This token only applies to areas 7 through 32,000.
path Absolute or relative pathname of each extent.
extentType Indicates whether the extent is fixed (f) or variable (v). If the extent type token is not specified, the extent is variable.

For variable-length extents, indicates whether the extent is extended (e), pre-extended (x), or whether it is extended or pre-extended with an imposed maximum size (ev) or (xv). For more information, see Extend variable-length database extents.
size Size of an extent in kilobytes. This value must be a multiple of 16 times your database block size.