Overview

This document provides guidance on the types and attribute values of key parameters related to Tibero Block and Memory.

Note

For more detailed Tibero parameter information, please refer to the attached file.

Method

Block

• DB_BLOCK_SIZE

This parameter sets the block size of the database. It must be set during the database creation stage and cannot be modified afterward.

Data block sizes typically used are 4KB for pure OLTP, 8KB for OLTP + batch processing, and 16KB or larger for DW, but generally 8KB is used.
However, it must be set to be greater than or equal to the OS block size.

The following explains advantageous block size settings depending on the situation.

Note

To check the filesystem block size on UNIX (or Linux), use the following command:
perl -e '$a=(stat ".")[11]; print $a'

Detailed information about the DB_BLOCK_SIZE parameter is as follows.

• DB_FILE_MULTIBLOCK_READ_COUNT

This parameter sets the number of blocks that can be read in one I/O operation.
Detailed information about the DB_FILE_MULTIBLOCK_READ_COUNT parameter is as follows.

• DB_MULTIBLOCK_PREFETCH_COUNT

This parameter sets the number of blocks to prefetch when reading disk blocks.
Detailed information about the DB_MULTIBLOCK_PREFETCH_COUNT parameter is as follows.

Memory

• DB_CACHE_SIZE

This parameter sets the size of the database cache buffer.
Generally, for single instances, it is set to about two-thirds of TOTAL_SHM_SIZE, and for TAC instances, about half. The appropriateness of the size is judged by the buffer cache hit rate.

 
Typically, an OLTP system is considered good if the hit rate is over 90%, DSS or DW systems over 80-85%, and purely batch processing systems may still function well even if the hit rate is below 50%.

Detailed information about the DB_CACHE_SIZE parameter is as follows.

• MEMORY_TARGET

This parameter sets the total memory used by the instance in bytes.
It is the sum of total shared memory and memory used by each process, calculated as TOTAL_SHM_SIZE + (total memory used by processes).

Detailed information about the MEMORY_TARGET parameter is as follows.

• TOTAL_SHM_SIZE

This parameter sets the total shared memory size used by the instance.

It consists of database buffers, redo log buffers, SQL cache, and data dictionary cache, and a certain level of memory must be allocated for the application to function properly.

Tibero typically configures TOTAL_SHM_SIZE to about 60-70% of the system's physical memory and adjusts it through monitoring later.

Detailed information about the TOTAL_SHM_SIZE parameter is as follows.

• LOG_BUFFER

This parameter sets the size of the memory area used to store logs.

Detailed information about the LOG_BUFFER parameter is as follows.