Berkeley DB: DbEnv::txn_stat
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++

# DbEnv::txn_stat |

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    #include <db_cxx.h>

    int
    DbEnv::txn_stat(DB_TXN_STAT **statp, void *(*db_malloc)(size_t));

# Description

The DbEnv::txn_stat method creates a statistical structure and copies a pointer to it into a user-specified memory location.

Statistical structures 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 returned memory, free the returned memory reference, references inside the returned 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:

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 the number of seconds since the Epoch, returned by the IEEE/ANSI Std 1003.1 (POSIX) time interface).
u_int32_t st_last_txnid;
  The last transaction ID allocated.
u_int32_t st_maxtxns;
  The maximum number of active transactions possible.
u_int32_t st_nactive;
  The number of transactions that are currently active.
u_int32_t st_maxnactive;
  The maximum number of active transactions at any one time.
u_int32_t st_nbegins;
  The number of transactions that have begun.
u_int32_t st_naborts;
  The number of transactions that have aborted.
u_int32_t st_ncommits;
  The number of transactions that have committed.
u_int32_t st_regsize;
  The size of the region.
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 DbEnv::txn_begin.
  u_int32_t parentid;
    The transaction ID of the parent transaction (or 0, if no parent).
  DbLsn lsn;
    The log sequence number of the transaction-begin record.

The DbEnv::txn_stat 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.

# Errors

If a fatal error occurs in Berkeley DB, the DbEnv::txn_stat method will fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, at which point all subsequent database calls will fail in the same way.

In addition, the DbEnv::txn_stat method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.

### Classes

DbEnv, DbTxn

# See Also

DbEnv::set_tx_max, DbEnv::set_tx_recover, DbTxn::abort, DbEnv::txn_begin, DbEnv::txn_checkpoint, DbTxn::commit, DbTxn::id, DbTxn::prepare and DbEnv::txn_stat.`

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