The fast mode threshold is used by the CA ADS runtime system in conjunction with the RESOURCES ARE FIXED specification to determine whether record buffers are written to disk or kept in main storage across a pseudo-converse. If the total size of all record buffers, in bytes, exceeds the fast mode threshold and RESOURCES ARE FIXED has been specified, the record buffers are written to disk; otherwise, the record buffers are kept in the storage pool. Storage used for currency blocks, CA ADS terminal blocks (OTBs), OTB extensions, and variable dialog blocks (VDBs) is not eligible for writing to scratch.
Size of the Threshold
The size of the threshold is a site-specific determination that is based on the availability of general resources versus the amount of available storage. I/Os for DC/UCF journaling and CPU cycles for record locking are used when record buffers are written to the scratch/queue areas. Therefore, when buffers exceed the fast mode threshold, the increased use of resources will slow down the transaction response time. On the other hand, if buffers are always under the threshold (that is, if the fast mode threshold is high), more memory is required.
Alternative Method
Alternatively, the DCA can specify that storage used for RBBs and statistics control blocks is always written to scratch across a pseudo-converse, regardless of the relocatable threshold that has been defined for primary and secondary storage pools. In this situation, other storage (that used for currency blocks, OTBs, OTB extensions, and VDBs) is written to scratch across a pseudo-converse only when the relocatable threshold is exceeded.
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