The Internal Interface may be used to specify an initial number of records for a variable. The pad value for the variable is written at each record as if the application had done so itself. The Internal Interface allows this to be done more conveniently with only one function call. Note that the default pad value for the variable's data type will be used unless a pad value is specified for the variable (also using the Internal Interface). If a specific pad value is desired for a variable, then it must be specified before the number of initial records is specified.
Specifying a number of initial records for a variable would usually be done only for a CDF with the single-file format. Because the records would be allocated contiguously within the CDF file, the indexing scheme (see Section 2.2.7) would require fewer entries making the access to that variable more efficient. Note that this method is not as efficient as allocating records in those cases where all of the records are going to be written by the application. (The records would be written twice. Once with the pad value and then again by the application.)
The number of initial records specified would in most cases be the number of records planned for a variable. Note that additional records may be added to a variable at any time. After the initial records are written with the pad value, the actual data values would be written by the application. Note that for NRV variables the number of initial records must always be specified as one (1). This is because at most only one physical record will ever actually be written.
Initial records are written to rVariables and zVariables using the <PUT_,rVAR_INITIALRECS_> and <PUT_,zVAR_INITIALRECS_> operations of the Internal Interface.