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How many categories of data types does Oracle have?

Oracle supports the following categories of data types:

Our organization utilizes the Oracle database and business operations require careful monitoring of the current redo log file?  Do you have any recommendations as how to we can efficiently perform these tasks? We also need to carefully monitor database uptime.

A query can be used to provide this information. It will indicate how capacity of the current redo log file and will project when the next log file will be archived out.

Code:

SELECT le.leseq                                "Current log sequence No",

         100*cp.cpodr_bno/le.lesiz           "Percent Full",

         cp.cpodr_bno                              "Current Block No",

         le.lesiz                                       "Size of Log in Blocks"

   FROM x$kcccp cp, x$kccle le

   WHERE le.leseq =cp.cpodr_seq

   AND bitand(le.leflg,24) = 8

  /

This code will help in addressing the uptime database issue.

SELECT to_char(startup_time,'DD-MON-YYYY HH24:MI:SS') "DB Startup Time"

 FROM   sys.v_$instance;

What are the differences between CHAR and NCHAR?

Both CHAR and NCHAR are fixed length character data types.

They have the following differences:

• CHAR's size is specified in bytes by default.
   

• NCHAR's size is specified in characters by default. A character could be 1 byte to 4 bytes long depending on the character set used. NCHAR stores characters in Unicode.

 Guideline:

 With Oracle dates can be converted to characters using the TO_CHAR() function:

 Example:

             SELECT TO_CHAR(SYSDATE, 'DD-MON-YYYY') FROM DUAL;

              -- SYSDATE returns the current date 17-MAY-2008

Will your courses help us to address specific issues relating to multi-vendor / multi-platform issues?