The Complete Guide to DBA Practices & Procedures - System Performance Part 10

Database Administration:
The Complete Guide to Practices and Procedures
Chapter 10
System Performance

The Larger Environment
• A DBMS operates within the context of a
larger environment.
• Other software and hardware components
must be installed, configured, and managed
effectively for the DBMS to function as
required.
– Tuning and configuring these components and
connections properly can have a dramatic impact
on system performance.
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Hardware Configuration
The hardware must be installed and set up properly for the
DBMS to operate efficiently.
• Is the computer hardware and capacity appropriate for the DBMS
environment?
• Is the computer firmware (e.g., ROM BIOS) up-to-date?
• Has a sufficient amount of memory been installed for all of the system
software to be installed (OS, DBMS, and other allied agents)?
• Has an appropriate amount of disk storage space been allocated and
configured for use by the DBMS?
• What type of disk storage is being used and is it appropriate for large data
volumes and high-speed database queries?
• Are all the network cables connected and functioning properly?
• Are all physical connections (e.g., cables, plugs, and board sockets) fully
connected and operational?
• Is the hardware connected to an uninterruptible power supply?
• Is the hardware connected to a surge protection device?

Components of the DBMS
• A DBMS is comprised of multiple programs that
deliver the requisite data management
functionality.
– Each program interoperates with other programs to
provide a database management system.
– Each DBMS breaks things apart a little bit differently
than others.
• The DBA must become an expert on the inner
workings of the DBMS in order to ensure an
optimized environment for database applications.

Memory Usage
• Relational databases love memory.
• The single biggest system performance tuning task that
a DBA will face is configuring RDBMS memory usage.
• The DBMS uses random access memory to cache data
and other resources required by the DBMS.
– Reading data from memory is much less costly than
reading the data from disk.
• The more memory you can provide to the DBMS, the
better performance will be.
– Of course, the DBMS has to be configured properly to use
the memory efficiently.

Data Cache
D
A
T
A
R
E
Q
E
S
T
O
R
S
Data Cache

Internal Structures Cache
• To accomplish relational operations, the DBMS
may need to create internal structures that
are not necessarily visible to the end user.
• However, DBAs, and sometimes programmers,
will need to know about the internal
structures.
• These internal structures are often cached
into memory as they are used.
– Example: DBD (database descriptor)

How Much Memory is Enough?
• This is a difficult question to answer.
• Have to balance cost of memory versus ROI of
the applications using the DBMS.
• At any rate, after calculating what you will
need to use based on the size and usage of
your database objects, it is always a good idea
to leave some breathing room.
– That is, add a little more memory than you think
you will need.

What if…
• Read efficiency is consistently below 80%?
• Consider:
– increasing the size of the data cache
– modifying the number or type of concurrent
processes using the data cache
– reducing the number of tables and indexes assigned
to the data cache
– create an additional backup cache (if possible)
– peg specific pages in memory
– automatically increase cache size based on processing
(if available)

All Transactions are Logged
LOG
1
2
CACHED
UPDATE INSERT DELETE
DATA
SQL
CACHED
UPDATE INSERT
DELETE
Database Logging

Are all Database Operations Logged?
• Depending on the DBMS, some operations may
not be logged.
• Examples:
– CREATE INDEX
– REORG
– Bulk Copy
– SELECT INTO
• There may be options for turning logging on and
off.
• Proceed with caution.

System Catalog Issues
• The physical location and setup of the system
catalog will have an impact on system
performance.
• The DBA must decide where it will be installed,
on what type of disk, and how much space to
allocate.
• These decisions typically are made at installation
time.
• Place the system catalog on a separate disk
device so that it can be managed and tuned
independently from other application data.

System Monitoring
• Use a system monitor.
– Built-in or third party
• A DBA must be able to operate and
understand the output of the monitoring
solutions available to him.
• The performance monitor acts as
a window into the efficiency of
the database system.

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The Complete Guide to DBA Practices & Procedures - System Performance Part 10

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The Complete Guide to DBA Practices & Procedures - System Performance Part 10