The list structure stores the actual shared variables across the Sysplex environment. The list structure requires from 0 through 4096 bytes per database row, depending on row contents. Each non-null column in a row requires 24 bytes of control information plus n bytes for the value itself. The maximum row length (the larger record in the Coupling Facility) is 4096 bytes.

The following formulas illustrate how to calculate the space requirements for the List structure:

• total_bytes = total-number-of-variables x 32 x 2

  Where

  total-number-of-variables = rows1 x cols1 x LPARs x db1 + rows2 x cols2 x db2

  and the values of rows, cols, and db are according to the number of rows, columns, and databases of Type 1 and Type 2.

  The required storage for each Type 1 list structure database is directly proportional to the number of LPARs (because there is a separate Type 1 database for each LPAR) and to the number of rows and columns.

  The required storage for each Type 2 list structure database is directly proportional only to the number of rows and columns.

  The number of variables in a database is equal to the number of columns times the number of rows.

  The total number of variables in all databases is equal to the sum of the variables in all Type 1 databases, plus the variables in all Type 2 databases.

  The total number of variables in all databases is multiplied by 32 because it is assumed that the average size of a variable is 32 bytes.

  The result is multiplied by 2 because each database needs temporary space for holding the entire database when a LOADGLOBAL operation is performed. See explanation below.

• blocks = total_bytes/1024 (rounded up to a multiple of 4)

  The result is divided by 1024 and then rounded up to next multiple of 4, since the space requested by CFRM policy is in units of 1 Kbytes, while the space required by Control-O/CMEM on startup is in units of 4Kbytes.

  Note: The definition of the maximum number of rows can be changed in the IOA ON-LINE PRIMARY OPTION MENU via the IV screen in ADMIN mode, with the U option for the database. The number of columns can be seen in the IV screen in ADMIN mode when selecting the database (pool).