IBM DB2 monitoring

Learn how to monitor IBM DB2 using the Dynatrace ActiveGate extension for IBM DB2.

Prerequisites

  • Environment ActiveGate
  • LUW distribution of IBM DB2
  • Host and port of the DB2 instance as well as user credentials to set up an endpoint for extension.
  • DB2 user with one of the following permissions: EXECUTE privilege on the routine, DATAACCESS authority, DBADM authority, or SQLADM authority

ActiveGate sizing

During initial testing an ActiveGate instance with 1 CPU and 2 GB RAM was used. Two DB2 instance endpoints were configured for the ActiveGate to monitor. The additional CPU load during extension invocation was measured at 5-10% with no noticeable increase in memory usage.

Extension installation

To install the extension

  1. Get the ZIP install file from your Dynatrace ONE Product Specialist via live chat. Don't rename the file.

  2. Unzip the ZIP file to the plugin_deployment directory of your Environment ActiveGate host.

  3. In Dynatrace, select Settings, Add new technology monitoring, and then Add ActiveGate extension.

  4. Select Upload extension and upload the ZIP file.

  5. After you upload the extension, go to Settings > Monitoring > Monitored technologies and switch to the Custom extensions tab.

  6. Find the extension and select it to open it for Endpoint configuration.

  7. Enter the endpoint information.

    Setting Details

    Endpoint name

    Enter a meaningful endpoint name. The name will only be visible on the configuration page.

    Connection host

    IP or DNS record pointing to your DB2 installation.

    Connection port

    Default = 50000

    Database name

    Name of the database through which the connection will be made.

    Connection user

    User through which the connection will be made. User must have read access to monitoring table functions. Example value for default installation of DB2: db2inst1. One of the following authorizations is required:

    • EXECUTE privilege on the routine
    • DATAACCESS authority
    • DBADM authority
    • SQLADM authority

    User password

    Use SSL for this connection

    SSL must be enabled on the server.

    Choose ActiveGate

    Select an Environment ActiveGate from the list.

Troubleshoot ActiveGate extensions

See Troubleshoot ActiveGate extensions.

Metrics

The following metrics are available.

System status

Metric name Metric description

AvailabilityPercent

Instance availability. Data points are reported as 100% for successful metric collection from instance and 0% in case of failure. Data points are later aggregated over the specified period of time.

ConnectionsCount

Number of connections. Amount of connections to the database since it’s been activated as obtained from TOTAL_CONS value.

Transactions

Metric name Metric description

ApplicationTransactionsCount

Number of application transactions executed. This provides an excellent base level measurement of system activity.

LogFLushTimePerTransactionRatio

The time an agent waits for log records to be flushed to disk. The transaction log has significant potential to be a system bottleneck, whether due to high levels of activity, or to improper configuration, or other causes. By monitoring log activity, you can detect problems both from the Db2 side (meaning an increase in number of log requests driven by the application) and from the system side (often due to a decrease in log subsystem performance caused by hardware or configuration problems).

TableReadsPerReturnedRowsRatio

Cache usage during transaction reads. This calculation gives an indication of the average number of rows that are read from database tables to find the rows that qualify.

  • Low numbers are an indication of efficiency in locating data, and generally show that indexes are being used effectively. For example, this number can be very high in the case where the system does many table scans, and millions of rows have to be inspected to determine if they qualify for the result set. Alternatively, this statistic can be very low in the case of access to a table through a fully qualified unique index. Index-only access plans (where no rows need to be read from the table) do not cause ROWS_READ to increase.
  • In an OLTP environment, this metric is generally no higher than 2 or 3, indicating that most access is through indexes instead of table scans. This metric is a simple way to monitor plan stability over time - an unexpected increase is often an indication that an index is no longer being used and should be investigated.

SortsPerTransactionRatio

The amount of sort operations per transaction. This is an efficient way to handle sort statistics, because any extra time due to spilled sorts automatically gets included here.

Locks

Metric name Metric description

LockFailsPerTransctionRatio

Lock fails (deadlocks and lock timeouts) per transaction. Although deadlocks are comparatively rare in most production systems, lock timeouts can be more common. The application usually has to handle them in a similar way: re-executing the transaction from the beginning. Monitoring the rate at which this happens helps avoid the case where many deadlocks or lock timeouts drive significant extra load on the system without the DBA being aware.

LockWaitPerTransactionRatio

Lock wait time per transaction. Excessive lock wait time often translates into poor response time, so it is important to monitor. The value is normalized to one thousand transactions because lock wait time on a single transaction is typically quite low. Scaling up to one thousand transactions provides measurements that are easier to handle.

Buffer pool

Buffer pool hit ratios, measured separately for data, index, XML storage object, and temporary data.

Buffer pool hit ratios are one of the most fundamental metrics and give an important overall measure of how effectively the system is exploiting memory to avoid disk I/O. Hit ratios of 80-85% or better for data and 90-95% or better for indexes are generally considered good for an OLTP environment, and of course these ratios can be calculated for individual buffer pools using data from the buffer pool snapshot.

Although these metrics are generally useful, for systems such as data warehouses that frequently perform large table scans, data hit ratios are often irretrievably low, because data is read into the buffer pool and then not used again before being evicted to make room for other data.

Metric name Metric description

PoolIndexPageHitsPercent

Index pages usage.

PoolDataPageHitsPercent

Data pages usage.

PoolXdaPageHitsPercent

XML storage object (XDA) pages usage.

PoolPhysicalReadsPerTransaction and PoolWritesPerTransaction

Pool physical reads and writes per transaction. These metrics are closely related to buffer pool hit ratios but have a slightly different purpose. Although you can consider target values for hit ratios, there are no possible targets for reads and writes per transaction. Why bother with these calculations?

  • Disk I/O is such a major factor in database performance, that it is useful to have multiple ways of looking at it.
  • These calculations include writes, whereas hit ratios only deal with reads.
  • In isolation, it is difficult to know, for example, whether a 94% index hit ratio is worth trying to improve. If there are only 100 logical index reads per hour, and 94 of them are in the buffer pool, working to keep those last 6 from turning into physical reads is not a good use of time. However, if a 94% index hit ratio were accompanied by a statistic that each transaction did twenty physical reads (which can be further broken down by data and index, regular and temporary), the buffer pool hit ratios might well deserve some investigation.

These metrics are not just physical reads and writes, but are normalized per transaction. This trend is followed through many of the metrics. The purpose is to decouple metrics from the length of time data was collected, and from whether the system was very busy or less busy at that time. In general, this helps ensure that similar values for metrics are obtained, regardless of how and when monitoring data is collected. Some amount of consistency in the timing and duration of data collection is a good thing; however, normalization reduces it from being critical to being a good idea.

PoolCleaningDirtyStealPerTransaction

Number of ‘dirty steal’ triggers per transaction. A "dirty steal" is the least preferred way to trigger buffer pool cleaning. Essentially, the processing of an SQL statement that is in need of a new buffer pool page is interrupted while updates on the victim page are written to disk. If dirty steals are allowed to happen frequently, they can have a significant affect on throughput and response time.

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