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Lesson 5. Saving performance data and working with saved data.

Don't overlook this feature. You can configure Lab128 to collect and store data automatically. You can save months of the most detailed performance data with continuous coverage and without the need of large disk storage. Thanks to compression, even very busy Oracle instances need no more than 4GB of disk space per month with all Lab128 features enabled. No other tools, including Oracle AWR, can provide this level of variety and time resolution. Does anyone need that level of performance data detail? Truthfully, you never know what kind of performance troubleshooting will be required. It can be a week until that someone will need to compare the load and resource usage, or will need to troubleshoot a query and will be tracking down changes over past days, weeks, or months. And often, you will need to troubleshoot events that happened hours or days ago. Lab128 addresses all these needs by saving performance data onto disk.

We are going to explain the best practices and strategies for saving performance data. It is assumed that you are using Lab128 on an NT-compatible computer running 24/7.

First, we should explain what data is stored in the .lab files. Lab128 keeps collected data in a ring buffer in memory. When the ring buffer becomes full, it continues collecting data while overwriting the oldest previously stored data. When you set the desired history length, the size of the ring buffer changes dynamically. The goal of automatic sizing is to allocate a buffer large enough to accommodate the specified history length. When performance data is saved onto disk, the contents of the ring buffer are dumped. The performance file also contains certain lookup tables, such as the names of statistics, names and IDs of database objects, names and IDs of database users, text of SQL statements, etc. Lab128 keeps all the ring buffer information compressed. When dumped onto disk, this data remains compressed. When opening the performance file, the reverse process takes place: the buffer in memory is populated from the file. The lookup tables are also restored. The data can be then viewed and explored as though it was in real-time. Obviously, the length of history stored in the performance file correlates to the size of the ring buffer. Therefore, setting the desired history length also affects the amount of history stored in the single performance file.

You can always save current data manually. In the Settings, you can specify a default directory where performance files should be saved. We suggest a dedicated directory per instance. When saving manually, you have the option to choose a folder other than the default one. When continuous coverage is required, you will need to make the next save before data is overwritten in the ring buffer. Therefore, the next file should slightly overlap with the previous one. It makes sense to run these saves automatically. This option can be toggled in Settings -> Saving Performance Data tab -> Autosave. The "Use suggested interval" check box sets the saving interval to one hour less than the History Length. We recommend you check this box and set Data History Length (Main Settings tab) to 9 hours (data will be saved every 8 hours) or 13 hours (data will be saved every 12 hours). This will simplify locating files when you need to view them later.

Opening and browsing stored files is straightforward. Most of the advice given for real time mode in previous lessons applies to exploring stored data. By default, the name of the file should include the name of the instance and date / time of the last data point it contains. This helps to locate the required file. As in real time mode, a typical sequence of troubleshooting actions includes Main window -> Individual Statistic charts -> Activity Explorer or SQL Explorer. Please see "Lesson 1. General Assessment of the State of Oracle Instance" for details.

Viewing and exploring performance data loaded from the file doesn't require an Oracle connection. The file can be moved and opened off-site; all it needs is another instance of Lab128. This creates an opportunity for practicing Oracle performance specialists and consultants to conduct performance analysis remotely without having access to the database.

Lesson summary. Lab128 can save current performance data onto disk. The file stores data in a proprietary compressed format. The "Data History Length" setting defines the history length stored in a single file. Use the Autosave option to automatically save data. For best results, set Data History Length to 9 or 13 hours.

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