Mizuho Bank said Thursday that Sunday’s system glitch, which led to the suspension of a huge number of its automated teller machines in Japan, was partly caused by work related to a data shift to digital passbooks.
In January, Mizuho Bank, the core unit of Mizuho Financial Group Inc., started digital bank account service, which does not issue paper passbooks, in an effort to cut costs and improve user convenience.
The digitalization shift may have put an excessive burden on the bank’s computer system, sources familiar with the matter said.
Mizuho Bank planned to complete the data shift work for digital passbooks by early March, but the glitch forced it to reschedule the task.
On Jan. 18, the bank started charging fees for paper passbooks for customers who newly open accounts, while launching digital account service allowing users to check their transactions online.
In line with the start of the new service, the bank is working on transferring data on accounts in which no record of transactions appears on passbooks for more than one year into digital accounts.
Mizuho Bank said regular data renewals of some 250,000 cases overlapped the work to transfer data into some 450,000 digital accounts on Sunday, leading to a capacity shortage at its core computer system.
As of Wednesday, Mizuho Bank had returned over 90% of the 5,244 cash cards and passbooks swallowed by ATMs hit by the glitch.
The bank also said that 29 cash cards and passbooks were swallowed by 29 ATMs, which were shut down Wednesday night due to another system problem.
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