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, u_int32_t flags);

# Description

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

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

DB_STAT_CLEAR
  Reset statistics after returning their values.

Statistical structures are created 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 library function 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 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_nrestores;
  The number of transactions that have been restored.
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 of the transaction.
  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

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. If a catastrophic error has occurred, the DbEnv::txn_stat method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DbEnv, DbTxn

# See Also

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

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