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Regenerate: Method to Expand the Capacity of a File Access Processor

IP.com Disclosure Number: IPCOM000034522D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 5 page(s) / 162K

Publishing Venue

IBM

Related People

Barnes, CC: AUTHOR

Abstract

The Storage Access System component of the File Access Processor (FAP) manages data blocks that comprise data files by mapping them to external devices. FAP is responsible for servicing requests on behalf of application support processors that submit requests to and receive responses from FAP using a connection-oriented communication protocol. The Control information is built during generation of the FAP, based on maximums defined by the user. These maximums have an effect on the size of control blocks in the Control information and determine how much data can be managed by the FAP. A serious problem existed if any of the limiting factors were reached. In order to expand the (Image Omitted) capacity of the Processor, the administrator had to start over by GENERATEing the processor again, specifying larger maximums.

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Regenerate: Method to Expand the Capacity of a File Access Processor

The Storage Access System component of the File Access Processor (FAP) manages data blocks that comprise data files by mapping them to external devices. FAP is responsible for servicing requests on behalf of application support processors that submit requests to and receive responses from FAP using a connection-oriented communication protocol. The Control information is built during generation of the FAP, based on maximums defined by the user. These maximums have an effect on the size of control blocks in the Control information and determine how much data can be managed by the FAP. A serious problem existed if any of the limiting factors were reached. In order to expand the

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capacity of the Processor, the administrator had to start over by GENERATEing the processor again, specifying larger maximums. However, there was no easy way to preserve the mapping of the user data, and reinstating all data files was a lengthy process.

The process consisted of: 1. Unloading all the user data to a backup device. 2. A larger control information device had to be allocated.
3. New maximums had to be established by GENERATEing the FAP. 4. All user data had to be reloaded. 5. All authorizations had to be re-established. This process was also disruptive to the end user because the FAP was unavailable until the five steps above were completed. The general layout of control information on the external device is shown in Fig. 1. Figs. 2 through 7 provide more detail for each control block in the control information. The variable length array in Master (Fig. 2) is a bit map index. There is one bit for each Allocation Bit Map block and it shows which block is active.

For example, the first bit being OFF would indicate Block 1 is the active block, and ON would indicate Block 1 prime is the active block. The size needed for the array is dependent on the size of the bit map structures. The administrator for the FAP controls the size of the two arrays contained in the External Array (Fig. 3) by means of a parameter at GENERATE which specifies the maximum number of external devices that will be associated with this processor.

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The Block Alternation Vector (Fig. 5) must map all blocks in the block map. The number of blocks needed for the block map is controlled by the administrator during GENERATE by a parameter which specifies the maximum number of users which are to be supported by this processor. The Summary Counters (Fig. 6) and Allocation Bit Maps (Fig. 7) are dependent on the size of the external device on which all the Control information resides. After reserving the space necessary for all the other control information, the remaining space is divided between these control blocks. There are three reasons for expanding the Control information and each one

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affects specific control blocks. The reasons are:

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1) Unable to allocate...