rvm_begin_transaction

NAME

rvm_begin_transaction - begin a transaction

SYNOPSIS

#include "rvm.h"

rvm_return_t rvm_begin_transaction (tid,mode)

rvm_tid_t    *tid;    /* pointer to transaction identifier */
rvm_mode_t   mode;    /* transaction begin mode */

DESCRIPTION

rvm_begin_transaction initiates a transaction. A unique transaction identifier is assigned and returned in the record specified by tid parameter. If the pointer does not reference a valid rvm_tid_t record, the RVM_ETID exception code is returned. If the transaction cannot be started because of internal memory limitations, RVM_ENO_MEMORY is returned.

rvm_begin_transaction recognizes two transaction modes: restore and no_restore. Transactions begun with restore create old value records so that the state of virtual memory can be restored if the transaction aborts. If mode is not a legal option, RVM_EMODE is returned.

The no_restore mode transactions do not create old value records. Therefore, an abort does not restore the state of virtual memory. They are offered as an additional performance enhancement for situations where there is no possibility that the application will issue an abort for the transaction.

Once a transaction is begun, modifications to mapped regions can be made with rvm_modify_bytes, or by the program in a range specified by rvm_set_range. The only restriction on modifications is that the modified regions must be mapped.

Transactions are ended with rvm_end_transaction, or rvm_abort_transaction, as appropriate.

DIAGNOSTICS

RVM_SUCCESS: success
RVM_ETID: invalid transaction identifier pointer
RVM_EMODE: illegal transaction mode
RVM_ENO_MEMORY: heap exhausted
RVM_ELOG: no log file has been specified
RVM_EINIT: RVM not initialized

AUTHOR

Hank Mashburn