Berkeley DB: DbTxnMgr::stat
Полезная информация


#include <db_cxx.h>

int DbTxnMgr::stat(DB_TXN_STAT **statp, void *(*db_malloc)(size_t));


method creates a statistical structure and copies pointers to it into user-specified memory locations.

Statistical structure are created in allocated memory. If db_malloc is non-NULL, it is called to allocate the memory, otherwise, the library function malloc(3)) is used. The function db_malloc must match the calling conventions of the malloc(3)) library routine. Regardless, the caller is responsible for deallocating the returned memory. To deallocate the returned memory, free each returned memory pointer; pointers inside the memory do not need to be individually freed.

The transaction region statistics are stored in a structure of type DB_TXN_STAT. The following DB_TXN_STAT fields will be filled in:

u_int32_t st_refcnt;
The number of references to the region.
u_int32_t st_regsize;
The size of the region.
DbLsn st_last_ckp;
The LSN of the last checkpoint.
DbLsn st_pending_ckp;
The LSN of any checkpoint that is currently in progress. If st_pending_ckp is the same as st_last_ckp there is no checkpoint in progress.
time_t st_time_ckp;
The time the last completed checkpoint finished (as returned by time(2)).
u_int32_t st_last_txnid;
The last transaction ID allocated.
u_int32_t st_maxtxns;
The maximum number of active transactions supported by the region.
u_int32_t st_naborts;
The number of transactions that have aborted.
u_int32_t st_nactive;
The number of transactions that are currently active.
u_int32_t st_nbegins;
The number of transactions that have begun.
u_int32_t st_ncommits;
The number of transactions that have committed.
u_int32_t st_region_wait;
The number of times that a thread of control was forced to wait before obtaining the region lock.
u_int32_t st_region_nowait;
The number of times that a thread of control was able to obtain the region lock without waiting.
DB_TXN_ACTIVE * st_txnarray;
A pointer to an array of st_nactive DB_TXN_ACTIVE structures, describing the currently active transactions. The following fields of the DB_TXN_ACTIVE structure will be filled in:

u_int32_t txnid;
The transaction ID as returned by DbTxnMgr::begin.
DbLsn lsn;
The log sequence number of the transaction-begin record.

The DbTxnMgr::stat method either returns errno or throws an exception that encapsulates an errno on failure, and 0 on success.


If a fatal error occurs in Berkeley DB, the DbTxnMgr::stat method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, at which point all subsequent database calls will also fail in the same way. Methods marked as returning errno will, by default, throw an exception that encapsulates the error information. The default error behavior can be changed, see DbException.

The DbTxnMgr::stat method may fail and throw an exception for any of the errors specified for the following Berkeley DB and C library functions: abort(3), fcntl(3), fprintf(3), getpid(3), malloc(3), and memset(3).



See Also

DbTxnMgr::begin, DbTxnMgr::checkpoint, DbTxnMgr::close, DbTxnMgr::open, DbTxnMgr::stat and DbTxnMgr::unlink.