I don't know? Did you?

EXEC msdb.sys.sp_helptext

@objname = N'dbo.sp_update_job';

I would not get into the habit of updating the tables in msdb directly. Here is a simpler way for you to produce the desired result next time you need to do something like this without using a cursor:

USE msdb;

DECLARE @sql NVARCHAR(MAX);

SET @sql = N'';

SELECT @sql = @sql + 'EXEC msdb.dbo.sp_update_job @job_name=N''' + name + ''',

@notify_level_eventlog=2,

@notify_level_email=2,

@notify_level_netsend=2,

@notify_level_page=2;

'

FROM msdb.dbo.sysjobs;

PRINT @sql; -- << output may be truncated but EXEC will execute complete content of variable

-- uncomment to exec

--EXEC(@sql);