Execute purpose functions

A single SQL command might involve a combination of the following purposes:

• Open a connection, file, or smart large object
• Create a table
• Scan and select data
• Insert, delete, or update data
• Drop a table
• Close the connection, file, or smart large object

A single oncheck request requires at least the following actions:

• Open a connection, file, or smart large object
• Check the integrity of a table
• Close the connection, file, or smart large object

The example in Partial sysams entry specifies only the am_getnext purpose for the super_access access method. A SELECT statement on a virtual-table that uses super_access initiates the following database server actions:

1. Gets the function name for am_getnext that the super_access entry in sysams specifies; in this case get_next_record().
2. Gets the external file name of the executable file from the get_next_record() entry in the sysprocedures catalog.
   The CREATE FUNCTION statement assigns the executable file as follows:

   Operating system	External executable-file name
   UNIX™ or Linux™	$INFORMIXDIR/extend/am_lib.bld(get_next_record)
   Windows™	%INFORMIXDIR%\extend\am_lib.bld(get_next_record)

3. Allocates memory for the descriptors that the database server passes by reference through get_next_record() to the access method.
4. Executes the am_getnext purpose function, get_next_record().