For many applications, it is not necessary to change the default values for the SOW storage parameters.
You may need to change the parameters if:
- You need to store larger messages than the default configuration allows (roughly 1MB)
- You want to control how the SOW file grows when more space is allocated
60East recommends using the following approach to configuring the SOW Storage parameters.
First, calculate the amount that you want the SOW to grow in a single allocation. You can use the message size and number of messages to calculate the growth size, or start with the desired growth size and message size to calculate the number of messages.
average size of messages * number of messages to allocate at once = growth size
Once you have that calculation, the changes to the configuration file depend on your version of AMPS.
For AMPS 5.0 and later
Set the SlabSize option in the Topic configuration to the growth size.
For AMPS versions previous to 5.0
Calculate an increment size by dividing the growth size / 128.
Set the RecordSize to 128 and the IncrementSize to the increment size calculated above. These versions do not have an explicit SlabSize option: instead, the product of RecordSize and IncrementSize is used as the SlabSize.
Important: The maximum message size for which AMPS will guarantee storage is the SlabSize. If the calculated value is smaller than the largest message size you need to store, 60East recommends increasing the SlabSize (using the method appropriate for your version) until the maximum size is large enough to store the largest anticipated message.
keywords: SOW storage, RecordSize, IncrementSize, SlabSize
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