The SQL Communication Area (SQLCA)

The SQL Communication Area (SQLCA) is an area of memory that is used on every database request for communicating statistics and errors from the application to the database server and back to the application. The SQLCA is used as a handle for the application-to-database communication link. It is passed in to all database library functions that need to communicate with the database server. It is implicitly passed on all embedded SQL statements.

A global SQLCA variable is defined in the interface library. The preprocessor generates an external reference for the global SQLCA variable and an external reference for a pointer to it. The external reference is named sqlca and is of type SQLCA. The pointer is named sqlcaptr. The actual global variable is declared in the import library.

The SQLCA is defined by the sqlca.h header file, included in the SDK\Include subdirectory of your installation directory.

• SQLCA Fields
  The fields in the SQLCA have the following meanings:
• SQLCA Management for Multithreaded or Reentrant Code
  You can use embedded SQL statements in multithreaded or reentrant code. However, if you use a single connection, you are restricted to one active request per connection. In a multithreaded application, you should not use the same connection to the database on each thread unless you use a semaphore to control access.
• Multiple SQLCAs
  You must not use the SQL preprocessor option (-r-) that generates non-reentrant code. Reentrant code is a little larger and a little slower because statically initialized global variables cannot be used. However, these effects are minimal.