Answer by devnull for Cron Job Not Running

Seems like you updated your post with more information, like Bruce said, that error tells you that ORACLE_HOME path is missing. Update your script to include:

export ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
export PATH=$PATH:$ORACLE_HOME/bin
export ORACLE_SID=IMR1

I would still fix this in your cron:

# run at 9:45 AM monday thur friday
45 09 * * 1-5 /home/oracle/scripts/tblspc_usage.sh >> /home/oracle/scripts/tblspc_usage.log 2>&1

• Append to log: >>
• Redirect stderr to log file (in this case same as stdout): 2>&1