Reviewing Berkeley DB log files
If you are running with transactions and logging, the db_printlog utility can be a useful debugging aid. The db_printlog utility will display the contents of your log files in a human readable (and machine-processable) format.
db_big: rec: 43 txnid 80000963 prevlsn 
The opening numbers in square brackets are the log sequence number (LSN) of the log record being displayed. The first number indicates the log file in which the record appears, and the second number indicates the offset in that file of the record.
The first character string identifies the particular log operation being reported. The log records corresponding to particular operations are described following. The rest of the line consists of name/value pairs.
The rec field indicates the record type (this is used to dispatch records in the log to appropriate recovery functions).
The txnid field identifies the transaction for which this record was written. A txnid of 0 means that the record was written outside the context of any transaction. You will see these most frequently for checkpoints.
Finally, the prevlsn contains the LSN of the last record for this transaction. By following prevlsn fields, you can accumulate all the updates for a particular transaction. During normal abort processing, this field is used to quickly access all the records for a particular transaction.
After the initial line identifying the record type, each field of the log record is displayed, one item per line. There are several fields that appear in many different records and a few fields that appear only in some records.
The following table presents each currently written log record type with a brief description of the operation it describes.
Augmenting the Log for Debugging
When debugging applications, it is sometimes useful to log not only the actual operations that modify pages, but also the underlying Berkeley DB functions being executed. This form of logging can add significant bulk to your log, but can permit debugging application errors that are almost impossible to find any other way. To turn on these log messages, specify the --enable-debug_rop and --enable-debug_wop configuration options when configuring Berkeley DB. See Configuring Berkeley DB for more information.
Extracting Committed Transactions and Transaction Status
Sometimes, it is helpful to use the human-readable log output to determine which transactions committed and aborted. The awk script, commit.awk, (found in the db_printlog directory of the Berkeley DB distribution) allows you to do just that. The following command, where log_output is the output of db_printlog, will display a list of the transaction IDs of all committed transactions found in the log:
awk -f commit.awk log_output
If you need a complete list of both committed and aborted transactions, then the script status.awk will produce it. The syntax is as follows:
awk -f status.awk log_output
Extracting Transaction Histories
Another useful debugging aid is to print out the complete history of a transaction. The awk script txn.awk allows you to do that. The following command line, where log_output is the output of db_printlog and txnlist is a comma-separated list of transaction IDs, will display all log records associated with the designated transaction ids:
awk -f txn.awk TXN=txnlist log_output
Extracting File Histories
The awk script fileid.awk allows you to extract all log records that refer to a designated file. The syntax for the fileid.awk script is the following, where log_output is the output of db_printlog and fids is a comma-separated list of fileids:
awk -f fileid.awk PGNO=fids log_output
Extracting Page Histories
The awk script pgno.awk allows you to extract all log records that refer to designated page numbers. However, because this script will extract records with the designated page numbers for all files, it is most useful in conjunction with the fileid script. The syntax for the pgno.awk script is the following, where log_output is the output of db_printlog and pgnolist is a comma-separated list of page numbers:
awk -f pgno.awk PGNO=pgnolist log_output
Other log processing tools
The awk script count.awk prints out the number of log records encountered that belonged to some transaction (that is, the number of log records excluding those for checkpoints and non-transaction-protected operations).
The script range.awk will extract a subset of a log. This is useful when the output of db_printlog is too large to be reasonably manipulated with an editor or other tool. The syntax for range.awk is the following, where sf and so represent the LSN of the beginning of the sublog you want to extract, and ef and eo represent the LSN of the end of the sublog you want to extract:
awk -f range.awk START_FILE=sf START_OFFSET=so END_FILE=ef END_OFFSET=eo log_output