 | Level: Introductory Dwaine Snow (dwsnow@us.ibm.com), Senior DB2 Product Manager, IBM
19 Apr 2004
Updated 10 Aug 2006 Just like a high performance sports car, a database requires some checks to keep it running optimally.
This article is broken down into tasks or checks that can be run at different intervals on your DB2® for Linux®, UNIX®, and Windows® database, to do just that. Learn when to monitor and what you should be doing daily, weekly, and monthly. Updated for DB2 9.
Introduction
While databases are becoming more and more self-aware and self-healing, they still require some monitoring to
keep them running as efficiently as possible. Just like your car, a database requires some checks to keep it
running optimally. This document is broken down into tasks or checks that you can run at different time
intervals to ensure that your DB2 databases are running optimally, and detect potential issues before they happen.
The first set of checks or tasks should be run every day to make sure there are no current or imminent problems. The second set should be run weekly to check for issues or problems that may have occurred during the week or are likely to occur in the coming week. The final set of checks or tasks need not be run every day or week, but should be run monthly to keep the system running without problems, and to prevent further issues in the event that a problem does occur.
Monitoring the system
There are a number of reasons that you should monitor your databases, however, the main reason is to ensure that no problems currently exist with the system or are imminent. It is always better to detect a problem and take actions to prevent it from happening than to have to react to a problem once it has happened. By monitoring your DB2 database systems as described in this article, you will be able to detect many problems before they happen, and maintain the performance of your system.
Monitoring tools available
You will typically need to combine DB2 and operating system monitoring in order to get the complete picture of what is happening on the database server. DB2 tools alone normally do not give the complete picture.
When capturing the information for analysis, make sure that the DB2 and operating system information is captured at the same time, as you cannot correlate information captured at different times.
Capturing the system information
When monitoring the system, take the snapshots over a period of time. Taking them for only a one or two minute
period will not give a real view of the system activity. I suggest that you take the snapshot every one to 5 minutes,
for a period of at least one hour.
Linux and UNIX Tools
For example, to capture the CPU, memory and other operating system usage information on UNIX or Linux
we use the tool vmstat. To capture the
The parameters of the vmstat and iostat command are as follows.
Parameter 1 The interval, in seconds, at which the tool captures the system information
Parameter 2 The number of times that the tool should capture the system information
To run vmstat and iostat and capture a snapshot every 5 minutes (300 seconds) for 8 hours (28,800 seconds)
you can run the following commands:
vmstat 300 28800 > vmstat.out
iostat -tx 300 28800 > iostat.out
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NOTE: the -tx option on iostat is not supported on all UNIX/Linux versions, but is useful since it embeds the
timestamp for when the snapshot was taken.
Also make sure to capture the snapshots are normal/average workload times as well as peak workload times.
While it is important to ensure the normal workloads are handled efficiently, it is also important to ensure
that the system can handle the peak workloads without overloading the server.
Windows Tools
On Windows, you can look at the CPU usage and memory usage in the Task Manager as seen below, but you
cannot capture this information into a file like you can with vmstat and iostat:
Figure 1. Windows Task Manager
DB2 tools
DB2 has a number of tools that can be used to monitor the activity of the databases and instances. These include:
- The Health Monitor / Health Center
- Snapshot Monitors / SQL Snapshot Functions
- Event Monitors
There are also other tools and logs available that provide information about the databases and instances including:
- The administration notification log
- This is a separate file on Linux and UNIX and incorporated into the Event Log on Windows.
- DB2DIAG.LOG
- Memory Visualizer
1. Health Monitor
In Version 8, DB2 introduced two new features to help you monitor the health of your DB2 systems:
the Health Monitor and the Health Center. These tools add a management by exception
capability to DB2 9 by alerting you to potential
system health issues. This enables you to address health issues before they become real problems that
affect your system's performance.
The Health Monitor runs on the DB2 server and continually monitors the health of the DB2 instance
and databases. If the Health Monitor detects that a user-defined threshold has been exceeded (for example,
the available log space has dropped below a set percentage of the total space available), or if it
detects an abnormal state for an object (for example, the DB2 instance is no longer running), the
Health Monitor will raise an alert.
When an alert is raised two things can occur:
- The alert notification will be sent.
- This can be sent by e-mail or to a pager
- Pre-configured actions can be taken.
- A CLP script or a Task Center task can be executed.
A health indicator is a system characteristic that the Health Monitor checks. The Health Monitor comes
with a set of predefined thresholds for these health indicators. The Health Monitor checks the state of your
system against these health-indicator thresholds when determining whether to issue an alert. Using the Health
Center, commands, or APIs, you can customize the threshold settings of these health indicators, and define who
should be notified and what script or task should be run if an alert is issued.
The Health Center provides the graphical interface to the Health Monitor. You use it to configure the Health
Monitor, and to see the rolled up alert state of your instances and database objects. Using the Health
Center's drill-down capability, you can access details about current alerts and obtain a list of
recommended actions that describe how to resolve the alert. You can also choose to follow a recommended
action right inside the tool. The Health Center is easily configured to show status line health beacons
and/or pop up a dialog box telling you that the Health Center has an object in alert status.
2. Snapshot Monitors / SQL Snapshot Functions
DB2 maintains data about its operation, its performance, and the applications that are accessing it. This data is maintained as the database manager runs, and can provide important performance and troubleshooting information. For example, you can find out:
- The number of applications connected to a database, their status, and which SQL statements each application is executing, if any.
- Information that shows how well the database manager and database are configured, and helps you to tune them.
- When deadlocks occurred for a specified database, which applications were involved, and which locks were in contention.
- The list of locks held by an application or a database. If the application cannot proceed because it is waiting for a lock, there is additional information on the lock, including which application is holding it.
- The list of SQL statements executed against a particular database, how many times they were executed, how many sorts were performed on behalf of the statement and the total amount of CPU time used by each statement.
- The number of sorts that have occurred and the number currently in progress.
Because the monitors do add some overhead to the system, the monitor switches can be enabled or disabled
independently. They can also be set for the entire instance, and all databases in the instance, or can be set
within a database session. If the monitor switches are enabled within a session, they are only 'active"
for that session, and a snapshot taken from another session will not capture the monitor information. If the
switches are enabled using the DB2 instance configuration parameters, they are enabled for all sessions, unless
explicitly turned off within a session.
To set the monitor switches within a session, use the UPDATE MONITOR SWITCHES command or the sqlmon() API.
For example, to enable buffer pool, lock, and dynamic SQL statement monitoring, turn on the monitor switches
using the following command:
update monitor switches using bufferpool on lock on statement on
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NOTE: You must have SYSADM, SYSCTRL, SYSMAINT or SYSMON(new in DB2 9) authority to
update the monitor switches and/or take a DB2 snapshot.
You can access the data that the database manager maintains either by taking a snapshot or by using an event
monitor. You can take a snapshot in one of the following ways:
- Using the GET SNAPSHOT command from the command line
- Calling the SQL Snapshot table functions
- Using the Control Center
- Write your own application, that makes the sqlmonss() API call.
3. Event Monitors
Once an event monitor has been created and activated, it will collect information about the database and any
database applications when the specified event occurs. An event is a change in database activity which can be
caused by one of the following:
- A database connect / disconnect
- A deadlock, or lock timeout
- A statement execution
- A transaction start or finish
An event monitor is created based on the type of event that you want it to detect and record. For example,
a deadlock event monitor waits for a deadlock to occur; and when one does occur it will collect and
record information about the applications and locks involved in the deadlock condition.
Event monitors are created using the CREATE EVENT MONITOR statement and will collect event information
only when they are active. An event monitor is activated and deactivated using the SET EVENT MONITOR STATE
statement. The EVENT_MON_STATE function will return the current state of the specified event monitor.
When the CREATE EVENT MONITOR statement is executed, the definition of the event monitor is created and
stored in the system catalog tables.
-
SYSCAT.EVENTMONITORS: Event monitors defined for the database.
-
SYSCAT.EVENTS: Events types being monitored for the database.
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SYSCAT.EVENTTABLES: The names of the target tables for table event monitors.
Operating system tools
Database tools / snapshots by themselves typically do not give you the complete picture of your
system performance. For example, a database may be 100% optimally tuned, but will not be able to
perform well if I/O contention is occurring on the server. Therefore it is important to look at the complete picture to make sure the entire system is performing well.
Daily procedures
Verify that all instances are up and running
This can be done in a number of ways:
- Use the Health Center.
- export/set DB2INSTANCE=instancename
- Attach to all instances.
- On UNIX or Linux, run ps -ef | grep db2sysc
- Verify there is one db2sysc process for each instance.
- On Windows, check that the service for each DB2 instance is started.
The attach method can be easily scripted as long as all of the instances (that is, NODEs) are cataloged on your workstation.
To use the ps command on UNIX and Linux you first need to telnet into each of the servers.
Verify that all databases are active or consistent
The definition of consistent can be confusing, and how it is reported by the GET DB CFG command often causes questions.
By definition, a database is consistent when all committed transactions have been written to disk, and any uncommitted transactions are not on disk When a database is running with applications connected to it, there will be transactions that have changed pages, that may have committed, but the changed pages may not have been flushed from the buffer pool to disk. Also, there may be transactions that were rolled back but their changes were flushed to disk. In this case the GET DB CFG will report that the database is inconsistent, but in fact it is fine. Therefore, simply getting the database configuration information for all databases is not sufficient.
A good method, because it will also make inconsistent databases consistent and therefore reduce the times for
future connect requests, is to successfully connect to all databases. This also can be easily scripted, as long as all of the databases are cataloged on your workstation.
Look for new Administration Notification Log and/or DB2DIAG.LOG entries
It is important to make sure that there were no problems that occurred overnight. Since Version 8, DB2 has been
writing diagnostic messages to two places, the Administration Notification Log (where the messages intended for DBAs
are written), and the DB2DIAG.LOG file (where the messages intended for the DB2 service team are written).
On Windows, the Administration Notification log is written to the Application Event Log and can be
viewed using the Event Viewer by choosing the Application log and looking for events written by the
application named DB2.
Figure 2. Windows Event Viewer
On Linux and UNIX, the log is written to a file named <instance_ID>.nfy that is located in the directory specified by the DIAGPATH instance level configuration parameter. To view the notification log you can:
- Connect to each of the servers using telnet or remote terminal services.
- For each instance, go to the DIAGPATH directory.
- At the command prompt:
- Run the tail command on the notification log to dump the last 100 entries
- Edit the file and look at the most recent entries at the bottom of the file.
Check that the previous night's backups were successful
There is nothing worse than having a problem on your system, and deciding to restore the most recent backup,
and then finding that the backup was not taken or is not complete. Therefore, it is important to check that the
previous night's backup(s) were successful and that they have been stored in a safe location.
The first step is to ensure that the backups were successful. This is done using the List History command
as follows:
list history backup all for db_name
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This can be scripted so that it is run for all databases after the backups complete, and the report
emailed to you. You can then simply verify the report each morning.
In the event that the whole server goes down for a sustained period of time, you may need to revert
to your disaster recovery plan, restore the database to another server, maybe in another location.
Therefore it is important that the backup images be stored in a safe site, not only on the server
where the backup is taken. This can be easily accomplished by copying the backup image to a LAN drive,
an NFS mounted drive or to a tape device.
Verify database logs have been archived successfully
If your database is read only, or can be rebuilt from scratch easily, you likely do not have log retain
enabled so you can skip this step. However, for those transactional databases where you can not afford to
lose any committed transactions, it is important to make sure log retain is enabled, and that the logs are
being archived successfully so that the database can be rebuilt and the transactions replayed in the event
of a disaster.
While recovery may be the primary reason for verifying the logs are being archived successfully, there is
another important reason. If the logs are not archived, they will remain in the LOGPATH. Since the LOGPATH is
normally on a file system with a set size, if the log files are not being archived, as new logs are created
the file system will be filled up. When this occurs, DB2 will be unable to create any more log files and
will therefore stop.
When a userexit is called to archive a log file, it will write information to two places. The first place
will be the userexit audit log where an entry will be written for every archive log request received by the
userexit. In the event of an error during the userexit processing, a message will be written to the userexit
error log file as well. These log files are in the LOGPATH and are named ARCHIVE.LOG and USEREXIT.ERR
respectively.
To examine these logs you can easily write a script to grab the last 50 to 100 lines from these files
(using the tail command) for all instances and email them to you. Then you can study them along with the
recovery history information each morning.
Check that no DBM and/or DB configuration parameters have changed
Whenever you work with other DBAs there is always a chance that someone else might have changed one or more
database or database manager configuration parameters and forgot to tell everyone else. Since changes
to the database and database manager configurations have a big impact on the system, veryify that they have not
changed unexpectedly. Capture the DB and DBM configurations into a file as follows:
get dbm cfg
get db cfg for db_name
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Make sure that you capture the output of the commands to a file, and name the file so that is has the date as
part of the name, like DB_DBM_CFG.07152006.out. Then you can use a tool like diff to compare the
current output with the previous day's output as follows:
diff DB_DBM_CFG.07142006.out DB_DBM_CFG.07152006.out
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This way, if there is a change you will see something like the following:
< Degree of parallelism (DFT_DEGREE) = 1
---
> Degree of parallelism (DFT_DEGREE) = 4
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Check important performance measures based on your workload
While the buffer pool hit ratio is very important for OLTP systems, it is impossible to have a high buffer
pool hit ratio in a database warehouse, so examine the measures that are important for your workload. Some of
the important performance measures, and how they can be calculated are shown below.
Calculate the data, index and combined buffer pool hit ratios as well as the asynchronous read percentage
using the following statement:
select substr(bp_name,1,20) as BP_NAME,
int (( 1 - (decimal(pool_data_p_reads) / nullif(pool_data_l_reads,0) )) * 100) as data_hit_ratio,
int (( 1 - (decimal(pool_index_p_reads) / nullif(pool_index_l_reads,0) )) * 100) as index_hit_ratio,
int (( 1 - (decimal(pool_data_p_reads + pool_index_p_reads) /
nullif( (pool_data_l_reads + pool_index_l_reads),0) )) * 100) as BP_hit_ratio,
int (( 1 - (decimal(pool_async_data_reads + pool_async_index_reads) /
nullif( (pool_async_data_reads + pool_async_index_reads + direct_reads),0) )) * 100) as Async_read_pct,
int (( 1 - (decimal(direct_writes) / nullif(direct_reads,0) )) * 100) as Direct_RW_Ratio
from table (snapshot_bp ('sample', -1) ) as snapshot_bp ;
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Note: The nullif function is used in the query above to return a null when the number inside the bracket
(i.e. pool_data_l_reads or pool_index_l_reads) is zero (0), otherwise the calculation would cause a divide by
zero error and the statement will fail.
Examine the usage patterns for the tables in your database using the query below. This query examine how many
rows were read, written, and the number of overflow records accessed using the following statement.
select
substr(table_schema,1,8) as Schema,
substr(table_name,1,30) as Table_Name,
rows_read,
rows_written,
overflow_accesses
from table (snapshot_table ('sample', -1) ) as snapshot_table;
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Examine the overall database usage patterns using the query below. This query examines:
- How many rows were read vs. selected
- How many lock waits occurred, the total lock wait time and the average lock wait time
- How many deadlocks and lock escalations were detected
- How many sorts occurred, the total sort time, and the average sort time, the percent of sorts that overflowed
select
db_name,
SNAPSHOT_TIMESTAMP,
rows_read,
rows_selected,
lock_waits,
lock_wait_time,
lock_wait_time/nullif(lock_waits,0) as avg_wt_time,
deadlocks,
lock_escals,
total_sorts,
total_sort_time,
total_sort_time/nullif(total_sorts,0) as avg_sort_time,
sort_overflows,
sort_overflows/nullif(total_sorts,0) as pct_ovflow_sorts
from table (snapshot_database (' ', -1) ) as snapshot_database;
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Check for automatic actions DB2 has taken on your behalf
With the growing ability for DB2 to adapt to changes in performance and usage automatically, much of the everyday
administration is no longer required, but you still might want to look at, and understand, the changes DB2 has made
to the database configuration parameters as well as to the underlying table space allocation.
You can track the changes to the table space allocation using the list tablespaces show detail command.
The changes made by the automatic self tuning memory are logged in files named stmm.#.log in the
stmmlog directory. This directory is under the SQLLIB directory for the instance owner in Linux and UNIX,
under the SQLLIB\Instance directory on Windows.
Ensure there is enough free memory
Another important thing to look at on the server is the memory usage of DB2 and the entire server. On Windows you can
determine the amount of RAM on the server by opening My Computer, and then selecting Help and About Windows.
In UNIX and Linux the command free will display the amount of real memory (RAM) on the system, and how much is
currently in use and available. In the case below there is 1GB of real memory on this server, and approximately 717MB is allocated
to applications.
total used free shared buffers cached
Mem: 1036248 717240 319008 0 60200 430736
-/+ buffers/cache: 226304 809944
Swap: 1048784 0 1048784
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Study DB2
Nothing is more valuable in the long run than that a DBA who is widely experienced, and as widely read as
possible. This study should include DBA manuals, magazines, newsgroups and mailing lists.
The comp.databases.ibm-db2 news group is a great place to learn from, and share information with, your
fellow DBAs.
For more detailed information you should also look for our DB2 Certification Guide series, as these books are very informative.
Weekly procedures
Look for new objects
It is important to know if people are creating new tables, indexes, stored procedures, etc. in your production
database. New objects typically indicate that a new application has been installed on the server and any new
applications and/or objects will impact the operational characteristics of your system.
In addition, new objects will consume space within the database, so it is important to identify these
objects before they grow too large and could potentially fill a table space. If these objects are not
created by a DBA, they very likely may have been created in the wrong table space, which can cause space
and/or performance issues.
There are a few alternatives available to check for any new objects within the system:
- Run db2look and write the report to a file every week.
- Check for differences between the new output and the previous week's output.
- Select object names from SYSCAT.TABLES, SYSCAT.INDEXES, SYSCAT.PROCEDURES
- Check for differences between the new output and the previous week's output.
For any differences, you determine the CREATOR of the object from the catalog table and track the information
back to the person that created the object.
Look for new or changed applications
Once you have optimized your database based on your current workload, there is nothing more frustrating
than getting a call that the database is not performing well, and finding that the poor performance was
caused by a new application, or changes to existing applications that no one told you about. Unfortunately,
this happens all too often. By monitoring your database for new and/or changed applications you can hopefully
detect these changes before they cause performance problems.
To look for new applications you can use the list applications show detail command. If you redirect
the output of this command to a file and keep these files for a period of time, you can compare the files every
week to see if a new application name suddenly appears in the output.
To look for changes applications you can see what SQL is running on your system over time, and look
for new SQL that has not been run previously. To do this you can create a table as follows:
create table SQLstmts
(stmt varchar(200),
tstamp timestamp not null with default)
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You can then retrieve the SQL statements from the current package cache and insert them into a table for
analysis using the following statement:
insert into SQlstmts (stmt)
select substr(stmt_text,1,200) as SQL_Stmt
from table (snapshot_dyn_sql ('sample', -1) )
as snapshot_dyn_sql
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You can then examine this table for any SQL statements that have not been executed previously using the statement:
select distinct stmt,
count(stmt),
tstamp from sqlstmts
group by stmt,
tstamp
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In the output of this statement, any statement with a count of 1, and the timestamp column showing the current date is one that has not been run previously.
Look for tables and/or indexes needing REORG
As you insert, update and delete rows in your tables, the data in the tables may need to be REORGed to:
- Re-cluster the data in the order of your most important index
- Remove free space interspersed throughout the table
- Remove overflow records
The reorgchk tool will check your tables and indicate which tables may need to be reorged. You
can run the reorgchk tool against a single table, all user tables, all tables in a specific schema, or
all system catalog tables. You can also indicate whether the tool should use the current statistics in the
catalog tables as a basis, or gather new statistics first.
To run the reorgchk tool against all of your tables, and ensure you are using the current
statistics, use the command:
reorgchk update statistics on table user
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You should redirect the output of this command to a file for further analysis.
When viewing the output of the reorgchk tool, find the F1, F2 and F3 columns for your tables, and the F4, F5, F6, F7, and F8 columns for your indexes. If there is an asterisk (*) in any one of these columns, that indicates that DB2 has calculated that your current table and/or indices currently breach that threshold.
It is important to note that for tables, if you see an asterisk in any of the columns, then you typically need to reorg the table. However, since many tables have more than one index, by definition if one of them is 100% clustered, the other indices will not be clustered. Therefore you need to investigate the index portion of the reorgchk output in more detail and consider all of the indexes on the table when determining whether or not to reorg the index.
The calculations for the measures used by reorgchk are:
F1: the percentage of rows that are overflow records. When this is greater than 5% there will be an asterisk (*) in the F1 column of the output.
F2: the percentage of used space on the data pages. When this is less than 70% there will be an asterisk (*) in the F2 column of the output.
F3: the percentage of pages that contain data that contain some records. When this is less than 80% there will be an asterisk (*) in the F3 column of the output.
F4: the cluster ratio, i.e. the percentage of rows in the table that are in the same order as the index. When this is less than 80% there will be an asterisk (*) in the F4 column of the output.
F5: the percentage of space that is used on each index page used for index keys. When this is less than 50% there will be an asterisk (*) in the F6 column of the output.
F6: the number of keys that can be stored on each index level. When this is less than 100 there will be an asterisk (*) in the F6 column of the output.
F7: the percentage of record IDs (keys) on a page that have been marked as deleted. When this is more than 20% there will be an asterisk (*) in the F7 column of the output.
F8: the percentage of empty leaf pages in the index. When this is more than 20% there will be an asterisk (*) in the F8 column of the output.
When reorganizing a table you can optionally specify which on which index DB2 should cluster the data.
To reorg the ORG table based on the ORGX index, use the command
reorg table org index orgx
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The DB2 optimizer uses database statistics to determine the optimal access plans for your SQL statements. When
you make significant changes to the amount of data, or to the data organization in your tables you should
use the runstats tool to capture new statistics and store them in the system catalogs. You should also be sure
to capture statistics for any new table or index.
To capture statistics for the ORG table, and its indexes you can use the command
runstats on table <schema>.org with distribution and detailed indexes all
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NOTE: You must specify the schema for the table when using the runstats command.
Look for tables and indexes needing RUNSTATS
You can check for any tables or indexes without statistics, or with statistics that are over 7 days old
using the following statements:
select substr(name,1,30),substr(creator,1,10),stats_time
from sysibm.systables
where stats_time < ((current timestamp) - 7 days)
or stats_time is null
select substr(name,1,30),substr(creator,1,10),stats_time
from sysibm.sysindexes
where stats_time < ((current timestamp) - 7 days)
or stats_time is null
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Look for the 10 most active tables
When considering which tables to run reorg or runstats on you should also consider the activity
on the tables. To find the 10 most read tables, based on the number of rows read, use the following statement:
select substr(table_schema,1,10) as tbschema,
substr(table_name,1,30) as tbname,
rows_read,
rows_written,
overflow_accesses,
page_reorgs
from table (SNAPSHOT_TABLE(' ',-1)) as snapshot_table
order by rows_read desc
fetch first 10 rows only
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To find the 10 most updated tables, based on the number of rows written, use the following statement:
select substr(table_schema,1,10) as tbschema,
substr(table_name,1,30) as tbname,
rows_read,
rows_written,
overflow_accesses,
page_reorgs
from table (SNAPSHOT_TABLE(' ',-1)) as snapshot_table
order by rows_written desc
fetch first 10 rows only
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These tables are also likely candidates for at least a runstats, if not a reorg and a
runstats.
Archive all alert logs and DB2DIAG.LOG files
It is good practice to clean up the diagnostic logs on a regular basis. In the event an error does occur,
you then do not need to go over 6 months of information in the logs, and the logs are a lot smaller and
easier to edit. Before purging the files, make a copy of them in case you want to go back at some time
in the future to investigate what was occurring on the system at a given time.
On Windows you can save the event log to another file in the Event Viewer by selecting the Action menu,
and then choosing the Save Log File As option. You can then purge the entries from the log by
selecting the Action menu, and then choosing the Clear All Events option.
NOTE: It is good practice to name the file with the current date to make it easier to look back at the files at a later date.
For the DB2DIAG.LOG file as well as the administration notification log file on Linux and UNIX, you should
compress these files, and name then with the current date in the file name as well.
On Linux or UNIX, you can tar the *.nfy and db2diag.log files together, and then use
either gzip or compress to reduce the size of the resulting file.
Check for software updates
It is always good to know if there are any updates to the software that you are running. If your system
is running smoothly, you may not want to apply all service to your server. By reading the information about
the fixes contained in the fixpak / service packs, you can make a more educated decision about whether or
not to apply the fixpack. If you are encountering issues, you can look at the fix descriptions to see if
one of the available fixes might be the solution to your problems.
From a DB2 perspective, the most important web site is the DB2 for Linux, UNIX, and Windows Technical
Support Page:
http://www-3.ibm.com/cgi-bin/db2www/data/db2/udb/winos2unix/support/download.d2w/WINV8FP
One way to be sure you find out when a new fixpak becomes available is to subscribe to DB2 Alerts at this site:
http://www-3.ibm.com/cgi-bin/db2www/data/db2/udb/winos2unix/support/db2alert.d2w/report
Monthly procedures
Look for indicators of exceptional growth
Review your tables and table spaces to see how much they have grown in the past month. By knowing how fast
the tables and table spaces are growing, and how much space is still available, you can detect potential
space issues before they happen.
You can retrieve the size of the table space and the amount of space available using the statement below.
select substr(tablespace_name,1,120) as TBSPC_NAME,
used_pages,
free_pages,
from table (snapshot_tbs_cfg ('sample', -1) ) as snapshot_tbs_cfg
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You can see how big each of your tables is by looking at the system catalog tables. As long as your
statistics are current, this information will be accurate. To get the size of your tables use the statement
select tabname,
npages
from syscat.tables
where tabname not like 'SYS%'
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NOTE: If statistics have not been captured for a table, it will have a value of -1 for npages.
Create a history table or a spreadsheet to store this information so that you can scrutinize the space usage
for your tables and table spaces over time. An easy way to do this is to create an export statement using the select
statements above, and create a delimted ASCII (DEL) file which you can then import directly into a spreadsheet.
Project future performance based on projected growth
Compare the information you have been gathering on the system level CPU, memory, network, and disk utilization,
as well as the DB2 object information that you have been gathering, to identify trends that could lead to contention
or a shortage of any of these resources in the future.
Based on your analysis of the above information, you can plan for these situations before they happen and take
actions to prevent these situations from occurring.
The following appendices contain useful scripts that can be used to monitor your system and database. Note that
these scripts were written in files that were run using the CLP, and therefore contain comments. The comments are
preceded by the double dashes (--) and need to be removed if you are running these commands directly on the command
line.
Appendix 1: Table space information script
--Create the table named tablespaceinfo to store information from the table space snapshots for analysis.
create table TablespaceInfo(
timestmp timestamp,
tablespace_name char(128),
pct_free int,
-- Percent of space free in the table space
type char(5),
-- SMS or DMS
contents char(5),
total_pages int,
-- total # of pages
usable_pages int,
-- useable pages, total - tag, etc..
used_pages int,
-- # of pages used
free_pages int,
-- # of free pages
page_size int);
-- page size |
-- Insert the snapshot info into the tablespaceinfo table to be stored for analysis.
insert into tablespaceinfo
select
current timestamp,
substr(tablespace_name,1,120) as TBSPC_NAME,
(case
-- We can calculate pct free for DMS table spaces only as total_pages is
set to 0 for SMS by this stmt...
-- Therefore, check if DMS, and then calculate pct_free as 1-
(used/total) * 100%
when tablespace_type = 0 then (int( (1- (decimal(used_pages) /
decimal(total_pages))) * 100) )
-- For SMS set pct_free to 100... Could set to any numeric value.
else 100
end) as pct_free,
(case
-- Display the table space type, i.e. DMS or SMS as a string, not the numeric
value in the info.
when tablespace_type = 0 then 'DMS'
when tablespace_type = 1 then 'SMS'
-- Only 0 and 1 are VALID, therefore return an error for anything else.
else 'Error'
end) as Managed_By,
(case
-- Display the type of data that can stored in the table space, i.e. TEMP,
LARGE/LOB OR ALL,
not the numeric value in the info.
when tbs_contents_type = 2 then 'TEMP'
when tbs_contents_type = 1 then 'LARGE'
when tbs_contents_type = 0 then 'ALL' end) as Data_Type,
-- Also return the total_pages using the heading ALLOCATED PAGES,
total_pages as allocated_pages,
usable_pages,
used_pages,
free_pages,
page_size
from table (snapshot_tbs_cfg ('sample', -1) ) as snapshot_tbs_cfg
order by pct_free;
select tablespace_name,
date(timestmp) as dte,
pct_free
from tablespaceinfo
group by tablespace_name, pct_free, timestmp ; |
 |
Appendix 2: Table space container information script
-- Report the containers, their size and type associated with each tablespace
-- Group by tablespace_name to get all containers for a table space together
-- as the containers will be unique in this report.
-- Set the database name to NULL to get info on currently connected
-- database.
select
substr(tablespace_name,1,12) as TBSPC_Name,
substr(Container_name,1,67) as Cont_Name,
(case
when container_type = 0 then 'SMS Directory'
when container_type = 6 then 'DMS File'
else 'DMS Device'
end) as Container_Type,
usable_pages
from table (snapshot_container (' ', -1) ) as snapshot_container; |
Appendix 3: Buffer pool - Table space information
-- Report the buffer pool name and size along with the size and name of each table space
-- assigned to the bufferpool. This can be used to help size the bufferpools more appropriately.-
-- Group by bpname first to get all table spaces for a bufferpool together as the table spaces
-- will be unique in this report.
select substr(b.bpname,1,12) as BufferPool,
b.npages as BP_Pages,
substr(t.tbspace,1,12) as TableSpace,
usable_pages as TBSPC_Pages
from table (snapshot_tbs_cfg ('sample', -1) ) as snapshot_tbs_cfg ,
syscat.tablespaces t, syscat.bufferpools b
where t.bufferpoolid = b.bufferpoolid
and t.tbspace = tablespace_name
group by b.bpname, t.tbspace, usable_pages, npages; |
Resources Learn
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Discuss
About the author | | | Dwaine R. Snow is a senior product manager for DB2 Data Server. In this role, he is helping to determine the future direction of the product and decide what functional enhancements need to be made to it to ensure that it meets customer requirements. Dwaine has worked in a DB2 services consultant role with IBM for a number of years. In this role, he has provided on-site assistance with DB2 database and application planning, project planning and execution, large complex OLTP and Decision Support system design, database and application design, and performance tuning, as well as client/server and legacy system integration. Dwaine has authored or co-authored numerous articles and books on DB2, including The Advanced DBA Certification Guide and Reference for DB2 Universal Database for Linux, UNIX, and Windows and Understanding DB2: Learning Visually with Examples, and has presented at conferences around the world.
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