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Time Dependent Data Locking Mechanism

IP.com Disclosure Number: IPCOM000088175D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Belady, LA: AUTHOR [+2]

Abstract

A technique for the sharing of files in an internal data memory, such as a random-access memory, wherein a unit of data in such memory is locked to other users whenever a user accesses such data. The technique involves the setting of a predetermined time limit on the lock for such accessed data in memory, whereby, at the end of the set time, the lock is automatically unlocked for other users to access the data in memory. The storage locking can be provided for the "read exclusive" or "record hold" operations at the closest possible level in association with the physical record in storage, namely the internal data memory as opposed to locking the CPU to the other users. The system definitions and special instructions are described below. SYSTEM DEFINITIONS: 1.

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Time Dependent Data Locking Mechanism

A technique for the sharing of files in an internal data memory, such as a random-access memory, wherein a unit of data in such memory is locked to other users whenever a user accesses such data. The technique involves the setting of a predetermined time limit on the lock for such accessed data in memory, whereby, at the end of the set time, the lock is automatically unlocked for other users to access the data in memory. The storage locking can be provided for the "read exclusive" or "record hold" operations at the closest possible level in association with the physical record in storage, namely the internal data memory as opposed to locking the CPU to the other users. The system definitions and special instructions are described below. SYSTEM DEFINITIONS: 1. Time Stamps TM - A time stamp word associated with a block of memory. TS - A time stamp word associated with a block of storage. TC - A register associated with a data channel. CL - A time clock. 2. Storage Lock (LS) - Lock word associated with a storage block which contains a unique program identifier plus TS. 3. Memory Lock (LM) - Lock word in memory. Also contains the TM of the storage block which i locked. 4. Base Time (BT) - Base Time register set to a base time, typically by an Initial Program Load (IPL) of the computer. 5. Flag Bit (F) - Flag Bit used in conjunction with a read reference to locked storage envelope. SPECIAL INSTRUCTIONS:

1. Reading from storage into memory for update purposes:

RSL, r, a, 1 -- If contents of LS = 0, read the record contained in block r into memory addressed by (a), and TS into memory addressed by (1). Set lock LS. Note: TS is automatically set to new value, current time, by reference to r.

If contents of LS do not equal 0, TS is compared with BT. If (CL - TS)> BT (threshold value), or is negative, data transfer is effected, LS is set and TS is recorded in LM as above.

If contents of LS do not equal 0 and (CL - TS) < BT (threshold value), NOT READY signal is returned to RSL.

2. Writing from memory into storage:

WLE, r, a, 1 -- Contents of memory addressed by (1), LM is ccmpared with LS of storage...