Browse Prior Art Database

Vertical Microcode Log

IP.com Disclosure Number: IPCOM000049622D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Lawlor, FD: AUTHOR [+2]

Abstract

The IBM System/38 Vertical Microcode (VMC) log (VLOG) provides means for recording information related to unusual occurrences in the System/38 VMC in a very efficient manner. It also provides for long term retention of basic information and short term retention of voluminous information such as dumps.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 57% of the total text.

Page 1 of 3

Vertical Microcode Log

The IBM System/38 Vertical Microcode (VMC) log (VLOG) provides means for recording information related to unusual occurrences in the System/38 VMC in a very efficient manner. It also provides for long term retention of basic information and short term retention of voluminous information such as dumps.

Fig. 1 shows the overall structure of the VLOG. Information in the control segment provides for control of concurrent insert and retrieval requests. The "note log" segment provides for entries up to 256 bytes in length. The "dump log" segment provides for entries longer than 256 bytes. The structure of the note and dump entries and their relationship is shown in Fig. 2. When either the note or dump log is full, it "wraps" and entry resumes at the beginning of the log.

The VLOG function provides interfaces to the system for inserting information and to the system and service functions for retrieval.

The VLOG was designed with special attention to its structure, atomicity, multi tasking and concurrent access in order to meet the following design objectives: 1. Low overhead to logging requesters.

2. Minimize problems when dumping the requesting task

(process).

3. Minimize modification to the resources and status of the

requesting task.

4. Alleviate storage problems for large dumps.

5. Alleviate scheduling/performance problems related to

low priority requestors.

6. Eliminate recursion and deadlock problems.

7. Isolate the requestor from possible logging failures or

delays.

8. Serialize inserts.

9. Allow concurrent retrieval and insert.

10. Allow portability of the log to other systems.

11. Provide a variable size, reusable log (wrap).

12. Provide long-term retention of basic activity

information.

13. Provide short-term retention of voluminous data

(e.g., dumps).

The design met these objectives by means of a separate insert task, atomicity controls, concurrency controls and VLOG structure.

The use of a separate, high priority insert task minimized the overhead and impact to the requestor, and provided insert serialization (objectives 1-8).

Atomicity controls ensure that entries would appea...