How to Fix ‘Warning: require_once() [function.require-once]: Unable to allocate memory for pool.’ Warning thrown at you while you were trying to login in your WordPress admin page.

Today I was trying to login to my website’s Admin page but I was stopped by following warning by WordPress’s

 

Unable to allocate memory for pool

 
Full warning summery was something like this:

 

Warning: require_once() [function.require-once]: Unable to allocate memory for pool. in /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php on line 1547

Warning: Cannot modify header information - headers already sent by (output started at /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php:1547) in /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php on line 678

Warning: Cannot modify header information - headers already sent by (output started at /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php:1547) in /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php on line 679

Warning: Cannot modify header information - headers already sent by (output started at /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php:1547) in /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php on line 680

Warning: Cannot modify header information - headers already sent by (output started at /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php:1547) in /nnn/000/000/mnt/111111/domains/domainname.com/html/wp-includes/pluggable.php on line 896

 
So after few searches online I found out that culprit is SPAM related logs stored by Akismet in MySQL database for every SPAM comments it detects & it deletes.

 
So Solution to this problems was something like this:

 

 
I login to ‘phpMyAdmin’ page on my server,

 
Then I selected ‘wp_commentsmeta’ table & at bottom of page or besides it’s name I selected ‘Empty’ this particular table then click ‘OK or YES’ on next prompt.

 

Tip: Empty all ‘commentsmeta’ table in your MySQL Database for all domains & sub domains.

 
I found out that ‘wp_commentsmeta’ table grown out to more than 3MB (3 Mega Bytes) in size which was causing load on MySQL server.

 
& Voila I was able to login to my WordPress Website’s Admin page again.

 
Hope it helps!

 
Thanks & Regards
Mandar Apte