Typical LogMiner Session Task 4: Start LogMiner

After you have created a LogMiner dictionary file and specified which redo log files to analyze, you must start LogMiner. Take the following steps:

Execute the DBMS_LOGMNR.START_LOGMNR procedure to start LogMiner.
Oracle recommends that you specify a LogMiner dictionary option. If you do not, then LogMiner cannot translate internal object identifiers and data types to object names and external data formats. Therefore, it would return internal object IDs and present data as binary data. Additionally, the MINE_VALUE and COLUMN_PRESENT functions cannot be used without a dictionary.

If you are specifying the name of a flat file LogMiner dictionary, then you must supply a fully qualified file name for the dictionary file. For example, to start LogMiner using /oracle/database/dictionary.ora, issue the following statement:
```
EXECUTE DBMS_LOGMNR.START_LOGMNR( -
   DICTFILENAME =>'/oracle/database/dictionary.ora');
```
If you are not specifying a flat file dictionary name, then use the OPTIONS parameter to specify either the DICT_FROM_REDO_LOGS or DICT_FROM_ONLINE_CATALOG option.

If you specify DICT_FROM_REDO_LOGS, then LogMiner expects to find a dictionary in the redo log files that you specified with the DBMS_LOGMNR.ADD_LOGFILE procedure. To determine which redo log files contain a dictionary, look at the V$ARCHIVED_LOG view. See "Extracting a LogMiner Dictionary to the Redo Log Files" for an example.

Note:

If you add additional redo log files after LogMiner has been started, you must restart LogMiner. LogMiner will not retain options that were included in the previous call to DBMS_LOGMNR.START_LOGMNR; you must respecify the options you want to use. However, LogMiner will retain the dictionary specification from the previous call if you do not specify a dictionary in the current call to DBMS_LOGMNR.START_LOGMNR.

For more information about the DICT_FROM_ONLINE_CATALOG option, see "Using the Online Catalog".
Optionally, you can filter your query by time or by SCN. See "Filtering Data by Time" or "Filtering Data by SCN".
You can also use the OPTIONS parameter to specify additional characteristics of your LogMiner session. For example, you might decide to use the online catalog as your LogMiner dictionary and to have only committed transactions shown in the V$LOGMNR_CONTENTS view, as follows:
```
EXECUTE DBMS_LOGMNR.START_LOGMNR(OPTIONS => -
   DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + -
   DBMS_LOGMNR.COMMITTED_DATA_ONLY);
```
For more information about DBMS_LOGMNR.START_LOGMNR options, see Oracle Database PL/SQL Packages and Types Reference.

You can execute the DBMS_LOGMNR.START_LOGMNR procedure multiple times, specifying different options each time. This can be useful, for example, if you did not get the desired results from a query of V$LOGMNR_CONTENTS, and want to restart LogMiner with different options. Unless you need to respecify the LogMiner dictionary, you do not need to add redo log files if they were already added with a previous call to DBMS_LOGMNR.START_LOGMNR.