DbEnv::txn_stat()
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## DbEnv::txn_stat()

    #include <db_cxx.h>

    int
    DbEnv::txn_stat(DB_TXN_STAT **statp, u_int32_t flags);

The `DbEnv::txn_stat()` method returns the transaction subsystem statistics.

The `DbEnv::txn_stat()` method creates a statistical structure of type `DB_TXN_STAT` and copies a pointer to it into a user-specified memory location.

Statistical structures are stored in allocated memory. If application-specific allocation routines have been declared (see DbEnv::set_alloc() for more information), they are used to allocate the memory; otherwise, the standard C library malloc(3) is used. The caller is responsible for deallocating the memory. To deallocate the memory, free the memory reference; references inside the returned memory need not be individually freed.

The following DB_TXN_STAT fields will be filled in:

- DB_LSN st_last_ckp;

  The LSN of the last checkpoint.

- 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 function).

- u_int32_t st_last_txnid;

  The last transaction ID allocated.

- u_int32_t st_maxtxns;

  The maximum number of active transactions configured.

- u_int32_t st_nactive;

  The number of transactions that are currently active.

- u_int32_t st_nsnapshot;

  The number of transactions on the snapshot list. These are transactions which modified a database opened with DB_MULTIVERSION, and which have committed or aborted, but the copies of pages they created are still in the cache.

- u_int32_t st_maxnactive;

  The maximum number of active transactions at any one time.

- u_int32_t st_maxnsnapshot;

  The maximum number of transactions on the snapshot list at any one time.

- uintmax_t st_nbegins;

  The number of transactions that have begun.

- uintmax_t st_naborts;

  The number of transactions that have aborted.

- uintmax_t st_ncommits;

  The number of transactions that have committed.

- u_int32_t st_nrestores;

  The number of transactions that have been restored.

- roff_t st_regsize;

  The size of the transaction region, in bytes.

- uintmax_t st_region_wait;

  The number of times that a thread of control was forced to wait before obtaining the transaction region mutex.

- uintmax_t st_region_nowait;

  The number of times that a thread of control was able to obtain the transaction region mutex 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 of the transaction.

  - u_int32_t parentid;

    The transaction ID of the parent transaction (or 0, if no parent).

  - pid_t pid;

    The process ID of the originator of the transaction.

  - db_threadid_t tid;

    The thread of control ID of the originator of the transaction.

  - DB_LSN lsn;

    The current log sequence number when the transaction was begun.

  - DB_LSN read_lsn;

    The log sequence number of reads for snapshot transactions.

  - u_int32_t mvcc_ref;

    The number of buffer copies created by this transaction that remain in cache.

  - u_int32_t priority;

    This transaction's deadlock resolution priority.

  - u_int32_t status;

    One of the following list of constants: TXN_ABORTED, TXN_COMMITTED, TXN_PREPARED, TXN_RUNNING.

  - u_int8_t gid[DB_GID_SIZE];

    If the transaction was prepared using DbTxn::prepare(), then gid contains the transaction's Global ID. Otherwise, gid's contents are undefined.

  - char name[];

    If a name was specified for the transaction, up to the first 50 bytes of that name, followed by a nul termination byte.

The `DbEnv::txn_stat()` method may not be called before the DbEnv::open() method is called.

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.

### Parameters

#### statp

The statp parameter references memory into which a pointer to the allocated statistics structure is copied.

#### flags

The flags parameter must be set to 0 or the following value:

- `DB_STAT_CLEAR`

  Reset statistics after returning their values.

### Errors

The `DbEnv::txn_stat()` method may fail and throw a DbException exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

#### EINVAL

An invalid flag value or parameter was specified.

### Class

DbEnv, DbTxn

### See Also

Transaction Subsystem and Related Methods

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