Log Block Size Operating Systems 512 bytes Solaris, AIX, Windows NT/2000, Linux, Irix, DG/UX, OpenVMS, NetWare, UnixWare, DYNIX/ptx 1024 bytes HP-UX, Tru64 Unix 2048 bytes SCO Unix, Reliant Unix 4096 bytes MVS, MPE/ix
The log block size is the unit for the setting of the log_checkpoint_interval, _log_io_size and max_dump_file_size parameters.
Therefore, it is an important constant to know.
If your operating system is not listed in the table above,
then you can find your log block size using the following query.
select max(lebsz) from sys.x$kccle;
The log block size can also be inferred from the system statistics in StatsPack reports. There is a 16 byte header for each log block, and the size of the data area is approximately the number of bytes of redo generated (redo size) plus the number of bytes of redo space left unused (redo wastage) divided by the number of log blocks written (redo blocks written). Thus the approximate formula is
16 + (redo size + redo wastage) / redo blocks written
This formula will commonly understate the log block size by a few bytes, because it does not allow for redo that has been generated but not yet written, and the redo size statistic is commonly a little inaccurate.
© Ixora Pty Ltd. All rights reserved.