A programmer reveals the results of an interview with his mother, who was an IBM mainframe COBOL programmer, to find out how the banking system works
Tom Jodel, who is himself a programmer, interviewed his mother, who works as an IBM mainframe COBOL programmer at a major bank, about banking systems.
Interviewing my mother, a mainframe COBOL programmer
Jodel's mother started in-house training at Nordea Bank in 1991. Various tests were conducted during the training, and Jodel's mother got terrible scores on psychological tests and multitasking tests. On the other hand, I got very good scores on other tests, such as IQ tests, and after training, I was assigned a position as a COBOL programmer on an IBM mainframe.
From a technical perspective, the position of IBM mainframe COBOL programmer is the most important position in the bank, and if the entire team quits the job, the bank could go bankrupt in a few weeks. . The team has a rotation system and is available 24 hours a day, seven days a week. He was sometimes called in the middle of the night on Sundays.
COBOL is an imperative, procedural language that has been object-oriented since 2002. There is no problem with the language itself, but in the context of mainframe programming, there is a problem that ``there are no young people with knowledge''. Jodel's mother was born in 1964 and was 52 years old in 2016, when the original blog was written, but she was still the second youngest member of the team. The youngest member is two years younger than Jodel's mother.
The IBM mainframe database is a hierarchical database that IBM built for the Apollo program.
Nordea Bank has been storing transactions in Db2 for seven years since 2009 to avoid writing to IMS as much as possible. Already 11 billion transactions have been stored in Db2, and the size of each transaction varies depending on whether it is an individual account or a corporate account, but if the average size is 1KB, that means approximately 11TB of data is stored in transactions alone. It will be. Furthermore, since transactions are required by law to be stored for 10 years, the amount of data is expected to increase in the future.
IMS stores most non-transactional information. Although it is difficult to estimate simply because the amount of data varies depending on the type of information, it is estimated to be much larger than the amount of data stored in Db2. Also, since some data is stored on tape, you may be instructed to load and save data from a specific tape while the program is running.
In modern programming, an integrated development environment (IDE) is often used, but in mainframe programming, a tool called ISPF , which can almost be called an OS, is used. ISPF is connected directly to the mainframe, so there is no such thing as a local development environment.
80% of Nordea Bank's systems are batch jobs, which run at specific times to perform some processing on data or send data to other banks or institutions. For example, if you purchase a bottle of cola, the purchase price is immediately debited from your account balance, but the money remains in the bank until the batch job is run. Batch jobs process gigabytes of data, and sometimes they process terabytes of data and take hours to complete. Batch jobs are usually executed at night, so while transactions between banks usually take a day to complete, remittances to the same bank are executed immediately.
Jodel posted this blog article on Reddit and Hacker News and asked for questions, saying, ``If you have any questions, ask your mother.'' Many of the results are posted on the original blog, so if you are interested, please check it out.
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