awk: too many output files 10 record number 12

Iam getting issue while trying to split the files. Can anyone help me with this ?

Sample content:

apple fruit
goa   fruit
tomato vegetable
tiger  animal 

Script:

 #!/bin/bash
 awk 'FNR==1 { hdr = $0; next }
    {
        if(!f[$2]) { print hdr >"file" $2".htm"; f[$2] = 1 }
        print >>"file" $2".htm"
    }' samplefile.txt

Could you please try following(untested since samples are not given), in case of sun o.s use /usr/xpg4/bin/awk OR /usr/xpg6/bin/awk(please refer comments in this answer for more details too).

Seems like OP was using OLD broken awk where close function was not working of following solution, so I have suggested OP to use xpg awk(s), later Ed sir confirmed that too.

#!/bin/bash
 awk 'FNR==1 { hdr = $0; next }
    {
        if($2 != prev){close(file)}
        file="file" $2 ".htm"
        if(!f[$2]) {print hdr > file; f[$2] = 1 }
        print >> file
        prev=$2
    }' samplefile.txt

OR try:

#!/bin/bash
 awk 'FNR==1 { hdr = $0; next }
    {
        file="file" $2 ".htm"
        if(file!=prev){close(prev)}
        if(!f[$2]) {print hdr > file; f[$2] = 1 }
        print >> file
        prev=file
    }' samplefile.txt