Fast Path Considerations

Several of the environments through which you can invoke the adapter provide access to Fast Path databases (see the summary chart in Summary Chart). If your site accesses Fast Path, it should have included certain parameters in the IMS control region startup procedure. You may need to know the values of the following parameters in order to access Fast Path through the adapter:

Parameters

Definition

BSIZ

Specifies the size of the Fast Path buffer. It should be large enough to handle the largest Fast Path record.

DBBF

Specifies the number of buffers (of size BSIZ) to be allocated. A formula for calculating DBBF follows this chart.

DBFX

Number of DBBFs IMS should page fix at startup time.

When you access Fast Path databases through the IMS region controller program DFSRRC00, you specify two additional parameters, NBA (Normal Buffer Allocation, the number of DBBFs that the DFSRRC00 region can use) and OBA (Overflow Buffer Allocation, the number of DBBFs that the DFSRRC00 region can use as overflow buffers). Initiating the XMI Server in BMP Mode: PARM='BMP,XMI,psbname', and Invoking the Interface in BMP Mode: PARM='BMP,FOCUS,psbname', discuss these parameters.

When you access Fast Path DEDB databases from the DBCTL environment, the CNBA parameter (included in the DRA Startup Table, discussed in Installation Instructions) identifies the number of Fast Path NBA buffers.

DBBF is determined by the following formula:

DBBF = CNBA + NBA + OBA + DBFX + (a 20-30% cushion)

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