Sun Java System Application Server Enterprise Edition 8.1 2005Q2 High Availability Administration Guide

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## Getting Device Information

Monitor free space in HADB data (disk storage) devices:

- Routinely, to check the trend in disk space use.

- As part of preventive maintenance: if the user load has increased and you want to resize or scale the database configuration.

- As part of scaling up the database: Before running `hadbm addnodes` to add new nodes to the system, check whether there is enough device space. Remember, you need around 40-50% free space on the existing nodes to add nodes.

- When you see messages in the history files and `server.log` file such as

  - `No free blocks on data devices`

  - `No unreserved blocks on data devices` .

Use the `hadbm deviceinfo` command to get information about free space in data devices. This command displays the following information for each node of the database:

- Total device size allocated, in MB (Totalsize).

- Free space in MB (Freesize).

- Percent of device currently being used (Usage)

The command syntax is:

    hadbm deviceinfo  [--details]
    [--adminpassword=password | --adminpasswordfile=file]
    [--agent=maurl]  [dbname]

The dbname operand specifies the database name. The default is `hadb`.

The `--details` option displays the following additional information:

- Number of read operations by the device.

- Number of write operations by the device.

- Name of the device.

See General Options for a description of other command options.

For more information, see hadbm-deviceinfo(1).

To determine the space available for user data, take the total device size, then subtract the space reserved for HADB: four times the `LogBufferSize` `+ 1%` of the device size. If you do not know the size of the log buffer, use the command `hadbm get logbufferSize`. For example, if the total device size is 128 MB and the `LogBufferSize` is 24 MB, the space available for user data is 128 – (4 x 24) = 32 MB. Of the 32 MB, half is used for replicated data and around one percent is used for the indices, and only 25 percent is available for the real user data.

The space available for user data is the difference between the total size and reserved size. If the data is refragmented in the future, the free size must be approximately equal to 50% of the space available for user data. If refragmentation is not relevant, the data devices can be exploited to their maximum. Resource consumption warnings are written to the history files when the system is running short on device space.

For more information about tuning HADB, see the Sun Java System Application Server Performance Tuning Guide.

##### Example 3–16 Example of getting device information

The following command:

    hadbm deviceinfo --details

Displays the following example results:

    NodeNO Totalsize Freesize Usage NReads NWrites DeviceName
    0      128       120      6%    10000  5000    C:\Sun\SUNWhadb\hadb.data.0
    1      128       124      3%    10000  5000    C:\Sun\SUNWhadb\hadb.data.1
    2      128       126      2%     9500  4500    C:\Sun\SUNWhadb\hadb.data.2
    3      128       126      2%     9500  4500    C:\Sun\SUNWhadb\hadb.data.3

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