>>>>> "ST" == Suresh Thalamati <[EMAIL PROTECTED]> writes:
ST> derby has two types of log files , one that works in RWS mode with a
ST> preallocated log file ,
What is RWS mode?
ST> and one which uses file sync with out preallocation. In case of
ST> preallocation , zeros are written to the log file to the length
ST> specified by the logSwitchInterval (Default is 1 MB) , it is also
ST> configurable by the user.
What determines which mode is used?
ST> This problem can also be fixed by writing dummy log record.
ST> Filelogger.redo() code has to be fixed to understand this, currently
ST> it looks at the logEnd only when a good log records is read.
I was thinking that the "dummy" log record should be a "good" log
record so that the current implementation of redo() need not change.
ST> Another possible solution I was thinking to identify whether a log
ST> switch is good or not is by writing a INT (4 bytes of zeros ) after
ST> log file initialization. As 512 bytes writes suppose to be atomic.
ST> if (log file length > = LOG_FILE_HEADER_SIZE(24) +4) then the log
ST> switch before the crash can be fixed as good one and fix the scan code
ST> to use the empty log file instead of writing to the previous log file.
I am not sure I understood this. Do you suggest writing the INT just
after the header? Would this work for preallocated log files? Would
not the length always be 1 MB (default) in that case?
--
Øystein
