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Teradata RDBMS Database Administration - NCR

NCR Teradata RDBMS Database Administration - NCR , 2004. - 616 p.
Download (direct link): teradatadatabaseadmin2004.pdf
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About System User DBC.Crashdumps

Dump Data Without FALLBACK Protection

Without fallback, when an AMP is down Teradata handles a dump as follows:

The system does not copy any raw PDE dump data from the dump device areas into Crashdumps until all AMPs are again online.

If the copy operation is already in progress when an AMP goes down, the system defers the copy operation until after a restart brings the AMP online.

Ad-Hoc Creation with DIPCRASH

DBC.Crashdumps should be listed in the response from a HELP USER DBC statement.

If it does not exist and you want to use it, run the Database Initialization Program (DIP) utility and execute the DIPCRASH script.

You can start the Database Initialization Program (DIP) utility from:

The Supervisor screen of the DBW

On Windows 2000, the Tools menu of the Teradata MultiTool window

Caution: Make sure DBC has enough space to create Crashdumps and still retain enough for a maximum-sized transient journal plus overhead.

The amount of PERM space allocated to DBC.Crashdumps is deducted from the currently available space of user DBC. For example:

IF user DBC.Crashdumps is created with . AND the current space of user DBC is . THEN after DBC.Crashdumps is created, the current space of DBC is .
CREATE USER CRASHDUMPS AS PERM=1000000 DBC Sum(MaxPerm)=5447664.26 DB Sum(MaxPerm)=4447664.26

To review DBC space, follow the procedure detailed under "Modifying DBC.Crashdumps Space" on page 10-13.

For detailed instructions on running DIP, see "Database Initialization Program (DIP)" in Teradata RDBMS Utilities.

For a summary of all the initialization program scripts, the objects they create, and how those objects are used, see "The DIP Utility" on page E-2.

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Teradata RDBMS Database Administration 10 - 11 Chapter 10: Handling Teradata Crashdumps

About System User DBC.Crashdumps

Calculating DBC.Crashdumps Space Requirements

As a general rule, DBC.Crashdumps should have enough permanent space on each node to accommodate three, or at least two, PDE dumps. NCR recommends that the MAXPERM for DBC.Crashdumps be large enough to hold three crashdumps.

On an MPP system, 500 MB per node (or 250 MB, if you have modified user Crashdumps for NO FALLBACK), should suffice as a starting number for reasonably heavy workloads. Multiply 1 GB or 500 MB by the number of nodes in your configuration, and double or triple the total based on how many dumps you want to retain at one time.

However, dumps vary in size so there is no way to predict in advance exactly how much space to allocate for DBC.Crashdumps. There is no guaranteed formula because there are many variables to take into consideration, such as:

The number of vprocs running per node

The number of nodes per TPA

The applications being processed at the time of the dump

Whether Crashdumps is still defined with FALLBACK

If the starting figures suggested above are not large enough, the best thing to do is run some tests and increase PERM again as required.

Modifying DBC.Crashdumps Space

Crashdumps is created in DBC by running the DIPCRASH script, which should have been done during installation (as explained in "About System User DBC.Crashdumps" on page 10-11). Crashdumps is created in DBC, which is the owning user.

When your configuration is operational, review the DBC.Crashdumps PERM allocation and if necessary modify it based on your total crashdump space requirements.

Because DBC is the owner of DBC.Crashdumps, the amount by which you modify Crashdumps PERM space is added to or deducted from the available space of user DBC. For example, if you increase DBC.Crashdumps space by 9200 bytes:

Crashdumps PERM Before Modification Crashdumps PERM After Modification
PERM = 10000 PERM = 19200

DBC SUM(MaxPerm) DBC SUM(MaxPerm)
Sum(MaxPerm) = 5447664.26 Sum(MaxPerm) = 5438464.26

10 - 12 Teradata RDBMS Database Administration

10 - 11 Chapter 10: Handling Teradata Crashdumps

About System User DBC.Crashdumps

Caution: If DBC does not have enough space to both increase DBC.Crashdumps plus contain a maximum-size transient journal, you need to free up space or add more disks.

To evaluate if you need to modify the PERM allocation in DBC. Crashdumps, follow this procedure:

Step Action

1 Calculate your total DBC.Crashdumps space requirement.

2 If you have not yet granted ALL privileges on user Crashdumps to your site administrative user, do so now:

Step Action
a Log on through BTEQ as user DBC.
b Enter the following SQL statement, replacing yourdbauser with the username of your database administrative user: GRANT ALL ON DBC.Crashdumps TO yourdbauser;
c Log off from the DBC session.
d Log on through BTEQ as your database administrative user.

3 Query the DBC.DiskSpace view to find the current MAXPERM for user DBC.Crashdumps:

SELECT DataBaseName, SUM(MaxPerm) FROM DBC.DiskSpace WHERE DataBaseName = Crashdumps;
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