Configuring Your System

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In Levels of Data Protection, we discussed various levels of data security.

When you configure your system, there are some additional questions to be answered:

• How do I divide the workload over several disks to get the best performance?

  TRANSDB and its shadows should preferably be on fast disks, see Performance Aspects of Shadowing.

• How much disk space do I need for shadowing?

  A shadow file occupies the same amount of disk space as the master databank file.

  In general, you will have problems if TRANSDB or LOGDB run out of disk space. When this happens the system cannot continue. Therefore, it is important to make sure that there is enough space for these databanks.

  How large TRANSDB grows depends on the number of transactions and how fast the background threads are able to perform the transactions on the shadows. When the transactions are performed on the shadows, the space in TRANSDB where they were stored is released.

  How large LOGDB grows depends on whether the LOG option is used and how often backups are taken and DROP LOG is performed, since DROP LOG clears LOGDB and releases space (but the file size remain unchanged).

Note: Try and keep the length of time the shadows are offline to a minimum. If you do not, you risk TRANSDB growing and filling the disk to capacity.

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