waitfor

Description

Specifies a specific time, a time interval, or an event for the execution of a statement block, stored procedure, or transaction.

Syntax

waitfor {delay time | time time | errorexit | processexit | mirrorexit}

Parameters

delay: instructs Adaptive Server to wait until the specified amount of time has passed, up to a maximum of 24 hours.

time: instructs Adaptive Server to wait until the specified time.

time: a time in one of the acceptable formats for date/time data, or a variable of character type. You cannot specify dates—the date portion of the date/time value is not allowed. You can use the datatype time for this information.

errorexit: instructs Adaptive Server to wait until a kernel or user process terminates abnormally.

processexit: instructs Adaptive Server to wait until a kernel or user process terminates for any reason.

mirrorexit: instructs Adaptive Server to wait for a mirror failure.

Examples

Example 1

At 2:20 p.m., the chess table is updated with my next move, and a procedure called sendmail inserts a row in a table owned by Judy, notifying her that a new move now exists in the chess table:

begin 
    waitfor time "14:20" 
    insert chess (next_move) 
        values ('Q-KR5') 
    execute sendmail 'judy' 
end

Example 2

After 10 seconds, Adaptive Server prints the message specified:

declare @var char (8)
select @var = "00:00:10"
begin 
    waitfor delay @var 
    print "Ten seconds have passed.  Your time 
        is up." 
end

Example 3

After any process exits abnormally, Adaptive Server prints the message specified:

begin
    waitfor errorexit
    print "Process exited abnormally!"
end

Usage

After issuing the waitfor command, you cannot use your connection to Adaptive Server until the time or event that you specified occurs.

You can use waitfor errorexit with a procedure that kills the abnormally terminated process, to free system resources that would otherwise be taken up by an infected process.

To find out which process terminated, check the sysprocesses table with sp_who.

The time you specify with waitfor time or waitfor delay can include hours, minutes, and seconds. Use the format “hh:mi:ss”, as described in “Date and time datatypes” on page 20 in Chapter 1, “System and User-Defined Datatypes” of Reference Manual: Building Blocks.

The following example instructs Adaptive Server to wait until 4:23 p.m:
```
waitfor time "16:23"
```
This statement instructs Adaptive Server to wait for 1 hour and 30 minutes:
```
waitfor delay "01:30"
```
Changes in system time (such as setting the clock back for Daylight Savings Time) can delay the waitfor command.
You can use waitfor mirrorexit within a DB-Library program to notify users when there is a mirror failure.

Standards

ANSI SQL – Compliance level: Transact-SQL extension.

Permissions

No permission is required to use waitfor.