#include <db_cxx.h>
 
int
DbEnv::failchk(u_int32_t flags);

The DbEnv::failchk() method checks for threads of control (either a true thread or a process) that have exited while manipulating Berkeley DB library data structures, while holding a logical database lock, or with an unresolved transaction (that is, a transaction that was never aborted or committed). For more information, see Architecting Data Store and Concurrent Data Store applications, and Architecting Transactional Data Store applications, both in the Berkeley DB Programmer's Reference Guide.

The DbEnv::failchk() method is used in conjunction with the DbEnv::set_thread_count() , DbEnv::set_isalive() and DbEnv::set_thread_id() methods. Before calling the failchk()method, applications must:

If any of these methods are omitted, a program may be unable to allocate a thread control block. This is true of the standalone Berkeley DB utility programs. To avoid problems when using the standalone Berkeley DB utility programs with environments configured for failure checking, incorporate the utility's functionality directly in the application, or call the DbEnv::failchk() method along with its associated methods before running the utility.

If DbEnv::failchk() determines a thread of control exited while holding database read locks, it will release those locks. If DbEnv::failchk() determines a thread of control exited with an unresolved transaction, the transaction will be aborted. In either of these cases, DbEnv::failchk() will return 0 and the application may continue to use the database environment.

In either of these cases, the DbEnv::failchk() method will also report the process and thread IDs associated with any released locks or aborted transactions. The information is printed to a specified output channel (see the DbEnv::set_msgfile() method for more information), or passed to an application callback function (see the DbEnv::set_msgcall() method for more information).

If DbEnv::failchk() determines a thread of control has exited such that database environment recovery is required, it will return DB_RUNRECOVERY. In this case, the application should not continue to use the database environment. For a further description as to the actions the application should take when this failure occurs, see Handling failure in Data Store and Concurrent Data Store applications, and Handling failure in Transactional Data Store applications, both in the Berkeley DB Programmer's Reference Guide.

In multiprocess applications, it is recommended that the DbEnv handle used to invoke the DbEnv::failchk() method not be shared and therefore not free-threaded.

The DbEnv::failchk() method may not be called by the application before the DbEnv::open() method is called.

The DbEnv::failchk() method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.