Easy to master the impact of Informix's various parameter settings on performance

Note: (You should use raw disk space and do not use file system space.) ）

Raw disk space means accessing a raw disk partition through a character-mode special file (a ' C ' that always appears in the first column shown in the Ls-l command), not a block-mode special file associated with disk space (the 1th column shown for the ls-l command is ' B '), Nor does it refer to the volume management control device and any other devices that are not original partitions of the disk.

UPDATE STATISTICS

This is very important. When the numerical distributions on the related columns change significantly, the data distribution and statistics can be updated when the update STATISTICS command is run properly.

Run update STATISTICS high on the indexed columns and use update STATISTICS MEDIUM for all other columns. Due to the low internal parallelism of the update STATISTICS processing, Therefore, updating statistics with multiple concurrent tasks can improve global throughput. You may need to increase the value of the DBUPSPACE environment variable.

Pre-read

is useful for non-parallel sequential scans (data only, indexed, indexed/data). Through onstat-p monitoring.

If the sum of the Ixda-ra,idx_ra and Da_ra is close to the ra-pgsused, increase the read-ahead parameters and, if their sum is much smaller than the ra-pgsused, reduce the corresponding parameters, usually keeping the ra_pages<=32, and making the Ra_ Threshold is approximately equal to half pa_pages.

OLTP and DSS

Characteristics of OLTP:

More users

High transaction rate

Transactions are relatively small in terms of data processing

Obvious page operations (insert/update/delete)

Fast data access through indexing

High use of buffer cache fast

Limited parallel scope

DSS Features

Involves a lot of data

Little write operations (except temporary space and data loading)

Relatively few users

Large, complex queries for handling large numbers of data

Access data primarily through sequential scans

A wide range of parallel

Disk Distribution and fragmentation

Options for disk Hardware:

High transmission speed, less positioning time

A large number of small plates is better than a small market

Avoid controller overload

Separating online disk space from other system operations

File system

Swap space

Separating physical and logical logs

For any online application environment with a large number of write operations (inserts, updates, deletes), the logical and physical logs should be placed on separate disks/controllers. Do not put any more data on the disk where the physical, logical logs are placed.

To put a logical log on a different disk

Avoid conflicts between logs in the current log