Target Journal Size
The alterdb command specifies the target journal size in the the following format:
alterdb dbname -target_jnl_blocks=n
where n is the number of blocks between 32 to 65536.
A journal file is closed and a new one is created when either a checkpoint is taken (actually, when the first write after a checkpoint is taken) or when the journal file fills.
The -target_jnl_blocks=n option of alterdb allows some control over when the logging system declares a journal file full. This parameter is known as the “target journal file size” because the exact size of a journal file cannot be easily predicted. The archiver closes off journal files, if they grow larger than the target number of blocks, only at the completion of an archive cycle. Longer archive cycles imply more variation in journal file sizes.
Upon successful completion of this command, a message is written to the errlog.log. The updated block value can be observed as the infodb parameter “Target journal size”.
The command takes effect immediately (or more accurately, the next time the archiver reads the configuration file).
The initial journal size (init_jnl_blocks) may be affected by this command.